Compression dictionary snapshot system and method

ABSTRACT

A system configured to generate a set of compression dictionary snapshots. The system can determine a subset of a set of compression dictionary definitions, the subset having a first subset comprising one or more definitions that have changed since a time of a previous snapshot and a second subset having one or more definitions associated with a predetermined portion of the dictionary. The system can further generate and store snapshots based at least in part on the determined subset of one or more definitions and determine a plurality of active snapshots from the set of snapshots such that the set of one or more definitions is included in the plurality of active snapshots.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application incorporates by reference for all purposes the fulldisclosure of co-pending U.S. patent application Ser. No. ______, filedconcurrently herewith, entitled “COMPRESSION DICTIONARY SYSTEMS ANDMETHODS” (Attorney Docket No. 0097749-632US0) and co-pending U.S. patentapplication Ser. No. ______, filed concurrently herewith, entitled“COMPRESSION DICTIONARY GENERATION SERVICE SYSTEM AND METHOD” (AttorneyDocket No. 0097749-658US0).

BACKGROUND

Providing digital content to consumers quickly is important for contentproviders. For example, content consumers increasingly expect digitalcontent such as web sites, images or documents to arrive quickly whenrequested or else the content consumer will become dissatisfied andchoose alternative content or an alternative content provider. On theother hand, content being provided to users is becoming increasingcomplex and therefore larger in size. Although networks that senddigital content have seen improved throughput over time, these networksare nonetheless stressed by the growing demand for digital content on avariety of user devices. Accordingly, systems and methods that compressdigital content for transmission over a network can be desirable becausesuch systems and methods can allow digital content to be provided tocontent consumers faster.

BRIEF DESCRIPTION OF THE DRAWINGS

Various techniques will be described with reference to the drawings, inwhich:

FIG. 1 illustrates an example of a server and user device that are eachassociated with a plurality of dictionaries;

FIG. 2 illustrates an example of base dictionary and a sub-dictionary;

FIG. 3 illustrates an example of snapshot updates of a dictionary and asliding window in accordance with an example;

FIG. 4 illustrates an example of a dictionary and an initial snapshot inaccordance with an example;

FIG. 5 illustrates an example of a dictionary and snapshot updates inaccordance with an example;

FIG. 6 illustrates an example of snapshot updating and a sliding windowin accordance with an example;

FIG. 7 is a block diagram that illustrates an example of performing asnapshot update in accordance with an example;

FIG. 8 is a data flow diagram illustrating communications between a userdevice, compression server and content server for compressing andpresenting content as a content image;

FIG. 9 is a data flow diagram illustrating communications between a userdevice and server for selecting and using a dictionary set to compresscontent and providing the compressed content to the user device;

FIG. 10 is a data flow diagram illustrating communications between auser device and server for selecting and using a dictionary set tocompress content and provide the compressed content to the user devicealong with one or more supplementary dictionary;

FIG. 11 is a block diagram illustrating an example method for selectingone or more dictionaries based at least in part on characteristics ofone or more of user device, network or user characteristics;

FIG. 12 is a block diagram illustrating an example method for replacinga used dictionary set during a user session based at least in part onchanges in at least one of user device, network and usercharacteristics;

FIG. 13 is a block diagram illustrating an example method for generatingand selecting candidate dictionaries;

FIG. 14 is a block diagram illustrating an example method for generatingcandidate dictionaries as a service;

FIG. 15 is a block diagram illustrating an example method for monitoringeffectiveness of a dictionary set and replacing the dictionary set witha newly generated dictionary set where a replacement threshold isexceeded; and

FIG. 16 illustrates an environment in which various examples can beimplemented.

DETAILED DESCRIPTION

This disclosure application relates to shared dictionaries, which canallow for compression of content being sent from a server to a userdevice. For example, the server can be associated with and have accessto a first set of one or more dictionaries that are local to the serverand the user device can be associated with a second set of one or moredictionaries that are local to the user device. At least a portion ofthese first and second dictionary sets can include the samedictionaries. In other words, the server and user device can share orhave dictionaries in common.

The server can compress content being sent to the user device using aset of dictionaries selected by the server and/or user device and thecontent can be received and decompressed at the user device. Forexample, the dictionaries can include a set definitions, where thedefinitions include strings of characters such as letter, numbers, orthe like, where identifiers for such definition are shorter than thedefinition. Accordingly, compression of content can include the serverreplacing portions of the content that match a definition with a shorteridentifier and at the user device, the identifier is replaced with thedefinition to decompress the content. This can be achieved because theset of dictionaries selected for communication between the server anduser device can define a common set of definitions.

In some examples, a compression dictionary can comprise a lookup tablewhere a plurality of symbols are associated with a plurality ofrespective definitions. In other examples, a definition of a dictionarycan be defined by a location and a length, or the like. For example, adictionary can comprise a long string of characters and an identifiercan include a beginning character and an ending character (e.g., adefinition could include “character 1314 through character 1397”).Additionally, in some examples, a definition can also include a modifierof a dictionary including an indicator of a repeat, filter, transpose,or the like. For example, a definition can include “characters1314-1397, and repeat characters 1388-1397 twenty times.”

In some examples, a set of one or more dictionaries can be selected foruse during a session based on criteria such as characteristics of thecontent requested, a user profile, the user device, network conditions,and the like. For example, where a user profile indicates that the userlikes to browse a certain type of website, a set of dictionaries can beselected for use during a session that is most effective for compressingcontent of such websites. In other words, a set of dictionaries used ina session can be selected based on anticipated browsing during thesession based on prior user browsing history. In further examples, theset of dictionaries being used during a user session can be changed,replaced or modified based on changes in the content requested, a userprofile, the user device; network conditions, and the like.

Dictionaries used can be interrelated including sub-dictionaries thatare dependent upon a base dictionary or another sub-dictionary. In someexamples, a base dictionary can be larger than sub-dictionaries and thesmaller sub-dictionaries can be used to augment or modify the basedictionary. For example, a set of sub-dictionaries can be selected foruse during a session that is tailored to various characteristics of thesession as discussed above.

In some examples, a set of dictionaries can be selected that are alreadyshared by the server and user device. In other examples, a set ofdictionaries can be selected where the user device does currently shareor locally have access to one or more dictionary of the set and suchmissing one or more dictionaries can be sent to the user device so thatthe user device has local access to the dictionaries.

Further examples include performing rolling snapshot updates of one ormore dictionary. The techniques described include obtaining a snapshotmanifest, incrementing a snapshot count, and determining first andsecond subsets of a set of one or more identifiers and associateddefinitions defined by the one or more dictionary. The snapshot manifestmay be a listing of a set of identifiers and associated definitionsdefined by the one or more dictionary. The listing may include locationinformation that indicates where the one or more identifiers andassociated definitions of the set of one or more identifiers andassociated definitions may be found within the dictionary, within arolling snapshot update, or at some other location. Thus, the locationinformation may include information that uniquely distinguishes eachsnapshot, dictionary, and one or more identifiers and associateddefinitions defined by the dictionary.

The snapshot count may be any method for keeping track of the current ormost recent snapshot update and the active snapshot updates within asliding window representing the maximum snapshot depth. For example, thesnapshot count may be a counter that is incremented for each snapshotupdate. Alternatively, the snapshot count may be a pointer that isupdated for each snapshot update, or may be information configuredaccording to some other scheme for keeping track of current and pastpartial and/or full snapshots of the dictionary.

A first subset of identifiers and associated definitions may be a subsetof the one or more identifiers and associated definitions of thedictionary that have changed or are new (referred to as an “incrementalset” or “change set”) since a time of a previous full snapshot orsnapshot update. A second subset of one or more identifiers andassociated definitions may include a proportion of set of the one ormore identifiers and associated definitions of the dictionary,regardless of whether the one or more identifiers and associateddefinitions in the second subset are new or have changed since a time ofthe previous snapshot. The proportion may be determined by the maximumsnapshot depth; for example, a maximum snapshot depth of five may resultin a second subset comprised of 20% (i.e., ⅕th) of the set ofidentifiers and associated definitions of the dictionary.

The second subset may comprise identifiers and associated definitionsmutually exclusive from previous second subsets for snapshots up to themaximum snapshot depth. In other words, for a maximum snapshot depth offive, the identifiers and associated definitions may be the first 20%portion of the one or more identifiers and associated definitions mayinclude different identifiers and associated definitions than thesecond, third, fourth, and fifth portions of identifiers and associateddefinitions, the second 20% portion may include different identifiersand associated definitions than the first, third, fourth, and fifthportions of identifiers and associated definitions, and so on.

The techniques described further include obtaining the first subset ofidentifiers and associated definitions and the second subset ofidentifiers and associated definitions from their respective locationsindicated by the location information in the manifest, generating asnapshot update of these identifiers and associated definitions, andstoring the snapshot update. The snapshot update may be one or morefiles containing copies of the identifiers and associated definitions.

In further examples, candidate dictionaries can be generated based on acorpus of content and one or more of the generated candidatedictionaries can be implemented for compressing content or can replace acurrent set of dictionaries being used. The corpus of content caninclude any suitable set of content including one or more content type,and in one example, the content corpus can comprise a stream of websitetraffic.

Multiple candidate dictionaries can be generated from a differentportion or subset of the full content corpus. The generated dictionariescan be compared by compressing the full corpus of content with each ofthe candidate dictionaries and identifying quality metrics, aneffectiveness score, or the like, for each candidate dictionary based oneach respective compression of the full corpus of content. The qualitymetrics of the candidate dictionaries can be compared and thedictionaries can be ranked or one or more candidate dictionaries can beselected based on various suitable criteria.

In some examples, an implemented dictionary can be monitored andcandidate dictionaries can be generated and compared to the currentlyimplemented dictionary based at least in part on quality metrics. Wherereplacement criteria are met or a replacement threshold is exceeded, acandidate dictionary can be implemented in place of the currentlyimplemented dictionary. In some examples, a company can monitor and/orgenerate dictionaries for its own purposes. In some examples, a companycan provide dictionary generation and/or monitoring as a service to aplurality of customers. In such examples, customers can identify acontent corpus, select effectiveness criteria, select a desireddictionary size, select a compression type, and the like.

In the preceding and following description, various techniques aredescribed. For purposes of explanation, specific configurations anddetails are set forth in order to provide a thorough understanding ofpossible ways of implementing the techniques. However, it will also beapparent that the techniques described below may be practiced indifferent configurations without the specific details. Furthermore,well-known features may be omitted or simplified to avoid obscuring thetechniques being described.

In one example, as illustrated in FIG. 1, a system 100 can comprise aserver 102 and a user device 104, which are operably connected via anetwork 106. The server 102 can include any suitable configuration ofone or more virtual or non-virtual server. Such a server can beimplemented in hardware, including a processor, memory, and the like.Although the user device 104 is illustrated in this example as being atablet computer, in further examples, the server can include varioussuitable devices including a laptop computer, e-reader, gaming device,desktop computer, wearable computer, home automation system, and thelike. The network 106 can comprise any suitable configuration of wiredand/or wireless networks including the Internet, a cellular network, asatellite network, a WiFi network, and the like.

As illustrated in FIG. 1, the server 102 can be associated with a set ofbase dictionaries 108, a set of primary sub-dictionaries 110 and set ofsecondary sub-dictionaries 112. The user device 104 can also beassociated with a set of base dictionaries 108, a set of primarysub-dictionaries 110 and set of secondary sub-dictionaries 112. Invarious examples, a dictionary can be associated with the server 102 oruser device 104 where that dictionary is stored locally or locallyaccessible to the server 102 or user device 104.

As illustrated in FIG. 1, the server 102 and user device 104 can beassociated with matching dictionaries, including base 108 and/orsub-dictionaries 110, 112. For example, the server 102 is shown beingassociated with a set of base dictionaries 108 that consists of basedictionaries A-N, a set of primary sub dictionaries 110 that consists ofbase dictionaries A-N, and a set of secondary sub-dictionaries 112 thatconsists of secondary sub dictionaries A-N. On the other hand, the userdevice 104 is shown being associated with base dictionaries 108A, 108C,and 108θ, primary sub-dictionaries 110B, 110π, and secondarysub-dictionaries 112C, 112Ω. Accordingly, in this example, both theserver 102 and user device 104 are associated with dictionaries 108A,108C, 110B, and 112C. In other words, these dictionaries are shared orin common.

As discussed in more detail below, the server 102 and user device 104can communicate more efficiently using a set of dictionaries 101 thatare mutually associated with the server 102 and user device 104. Inother words, where the server 102 and user device 104 are bothassociated with copies of one or more of the same dictionary 101, theserver 102 and user device 104 can use these one or more shareddictionaries 101 to communicate more efficiently via the network 106.

Additionally, where the server 102 and user device 104 do not both havecopies of the same dictionary 101, such a dictionary 101 can be sharedvia the network 106. For example, in the example of FIG. 1, the userdevice 104 does not initially have a copy of primary sub-dictionary 110Dand secondary sub-dictionary 112F, so these dictionaries 101 can be sentto the user device 104 from the server 102. Sharing additionaldictionaries 101 can be desirable in various examples because some setsof one or more dictionaries 101 can provide for more efficientcommunication compared to other sets of dictionaries 101.

Shared dictionaries 101 and sets of dictionaries 101 can be related invarious suitable ways to provide for more efficient communication over anetwork 106. For example, FIG. 2 illustrates an example dictionary set200 comprising a primary dictionary 202 and a secondary dictionary 204.Both dictionaries are illustrated as including a set of identifiers 206,which are respectively associated with a definition 208. For example theidentifier 206 of “1” corresponds to the definition 208 of “String 1.”In various examples, the length or size of identifiers 206 is shorter orsmaller than the associated definition 208. Accordingly, communicationscomprising identifiers 208 can be smaller or shorter than communicationsusing the definitions 208 alone. For example, communication packets sentvia Internet Protocol (IP) can have a smaller payload by usingidentifiers 208, which can be decoded at a receiver using a shareddictionary that defines which identifiers 206 correspond to givendefinitions 208.

In various examples discussed in this disclosure (e.g., FIGS. 1 and 2),one or more shared dictionaries 101 can be used to encode and decodecommunications between a server 102 and user device 104. In one example,a single shared base dictionary 108 can be used by the server 102 anduser device 104 to encode and decode communications. However, in furtherembodiments, a single shared base dictionary 108 and one or more sharedsub-dictionaries (e.g., one or more primary sub-dictionary 110 and/orsecondary sub-dictionary 112) can be used to encode and decodecommunications between the server 102 and user device 104.

In some examples, a primary sub-dictionary 110 can be dependent upon oneor more base dictionary 108. For example, as illustrated in FIG. 2, thefirst dictionary 202 can be a base dictionary 108 having 1-N identifiers206 with corresponding 1-N string definitions 208, where “N” representsa positive integer. The second dictionary 204 can be a primarysub-dictionary 110 that is dependent on the first dictionary 202, whichincludes N+1, N+2, and N+3 identifiers 206 with corresponding N+1, N+2,and N+3 string definitions 208. In other words, in this example, thesecond dictionary 204 can be inoperable alone and the set of the firstand second dictionary 202 can be required to encode and decodecommunications between the server 102 and user device 104. However, ifonly the first dictionary 202 is shared by the server 102 and userdevice 104, the first dictionary 202 alone can be used to encode anddecode communications between the server 102 and user device 104.

Dictionaries 101 can be interdependent in various suitable ways inaccordance with further examples. Referring to FIG. 1, in one example,primary sub-dictionary 110B can be dependent upon base dictionary 108Aand secondary sub-dictionary 112C can be dependent upon primarysub-dictionary 110B. In other words, the shared set of base dictionary108A alone; or the shared set of set of base dictionary 108A and primarysub-dictionary 110B; or the shared set of base dictionary 108A, primarysub-dictionary 110B, and secondary sub-dictionary 112C would be operableto encode and decode communications between the server 102 and userdevice 104. However, other shared sets of base dictionary 108A, primarysub-dictionary 110B, and secondary sub-dictionary 112C would beinoperable to encode and decode communications between the server 102and user device 104.

Dictionaries 101 can have multiple dependencies in various examples. Inone example, primary sub-dictionary 110B can depend from either of basedictionary 108A or base dictionary 108C. In another example secondarysub-dictionary 112C can depend from either of primary sub-dictionary110B and primary sub-dictionary 110D. Additionally, although FIG. 1illustrates only primary and secondary sub-dictionary 110, 112 levels,in further examples, there can be any suitable number of levels ofsub-dictionaries, including sub-dictionaries that are tertiary,quaternary, quaternary, quinary, senary, septenary, octonary, nonary, orthe like.

As illustrated in FIG. 2, a dictionary set 200 can comprise a set ofconsecutively numbered identifiers 206 that each correspond to a stringdefinition 208. However, in further examples, identifiers 206 may not beconsecutively numbered or otherwise ordered. Additionally, identifiers206 may comprise any suitable plurality of numbers, letters, characters,or the like. String definitions 208 can comprise any suitable pluralityof numbers, letters, characters, or the like. In some examples, a stringcan comprise binary, text (e.g., one or more word, sentence), a uniformresource identifier (URI), a media access control (MAC) address, aportion of code (e.g., HTML, Java script), code corresponding to aportion of an image, code corresponding to a portion of an audiorecording, code corresponding to a portion of a video, or the like.

In further examples, a definition 208 may not be a string of letters,number and/or characters. For example, a definition can include animage, audio data, video data, a webpage snapshot, or the like. In oneexample, a dictionary can reference cached files or other content thatis stored on a user device and/or server.

As illustrated in FIG. 2, in some examples, a second dictionary 204 canadd additional identifiers 206 and definitions 208 to the set ofidentifiers 206 and definitions 208 present in a first dictionary 202.More specifically, this example illustrates the first dictionary 202having 1−N identifiers 206 that respectively correspond to 1−N stringdefinitions 208 with the identifier 206 of N+1, N+2, and N+3 being addedthat respectively correspond to N+1, N+2, and N+3 string definitions208.

However, in further examples, further dictionaries can modifydefinitions of a base dictionary or of another dictionary from which thedictionary depends. Referring to FIG. 1, a primary sub-dictionary 110can modify one or more definition of a base dictionary 208. In otherwords, a primary sub-dictionary 110 can replace one or more definitionof a base dictionary 208 with a new definition and/or add newidentifiers and definitions. Similarly, a secondary sub-dictionary 110can modify one or more definition of a base dictionary 208 and/or aprimary sub-dictionary 110.

In some examples, a dictionary can comprise a plurality of definitionswithout identifiers explicitly being defined by the dictionary.Identifiers can reference various portions of a dictionary based on astructure of the dictionary. For example, a dictionary can comprise astring of characters such as numbers, letters, and the like, and anidentifier can include a beginning character and an ending character(e.g., a definition could include “characters 1314-1397”). In anotherexample, a dictionary can include a plurality of rows with each rowincluding a string of characters and an identifier can include abeginning row and character number and an ending row and characternumber. Additionally, an identifier can include a modifier of such oneor more identified portion of the dictionary, including a repeat,filter, transpose, subtraction, multiplication, addition, or the like.For example, a definition can include “characters 1314-1397, and repeatcharacters 1388-1397 twenty times.”

Accordingly, in various examples, definitions can be overlapping orinclude some or all of the same portions of a dictionary as otherdefinitions. For example, where a dictionary includes the string“HELLOWORLD” a first definition could include the full string“HELLOWORLD,” a second definition could include the string “HELLO,” athird definition could include the string “WORLD,” and the like.

Additionally, in further examples, sub-dictionaries can be generated assnapshot dictionaries that serve to capture changes to one or more baseand/or sub dictionary over time. For example, FIG. 3 depicts a techniquefor snapshotting a changing base dictionary 302 (or set of dictionaries)by capturing snapshot updates 304A-304B over time. In some examples, a“snapshot update” may refer to copy of a portion of a dictionary at aparticular point in time. A snapshot update of the present disclosuremay include incremental data (which may also be referred to as a “changeset”) that includes data that is new or has changed since a previoussnapshot (full snapshot or snapshot update) was captured.

In some examples, the incremental data is caused to be pushed from thedictionary by an administrator or user of the dictionary (e.g., via anapplication programming interface call) to one or more system storingthe snapshots of the present disclosure, which can include a userdevice, server, or the like. In other implementations, the systemperforming the snapshot updating is authorized and configured to copythe incremental data directly from the dictionary on its own.

The snapshot update may further include a “proportional” portion (whichmay be referred to as a “mandatory set”) which may include a copy of acertain portion or proportion of the entire dictionary. In otherexamples, the system performing the snapshot updating is configured toobtain the proportional portion directly from the dictionary.Additionally or alternatively, in some implementations, the systemperforming the snapshot updating can obtain the proportional portionfrom previous snapshot updates. In some examples, the “proportion” ofthe proportional snapshot can vary from snapshot to snapshot.

Each of the snapshot updates 304A-304B can be seen to have been capturedat a different point in time. For example, the first snapshot update ofthe snapshot updates 304A-304B can be seen as being captured at time t₁,the second snapshot update of the snapshot updates 304A-304B can be seenas being captured at time t₂, and so on up to the most recent capturedsnapshot of the snapshot updates 304A-304B captured at time t₁₆. In someexamples, the term “snapshot depth” (which may also be referred tosimply as “depth”) may refer to how many snapshot updates 304A-304B, atmost, will be needed for obtaining the base dictionary 302 at a currentstate; in other words, the snapshot depth reflects the size of thesliding window 306, and may be a predetermined value that acts an upperlimit to the number of active snapshots 304B in the sliding window 306.The representation of FIG. 3 shows one example 300 of the presentdisclosure having a snapshot depth of six; that is, the example 300 isconfigured such that the current state of the changing base dictionary302 can be obtained using only six consecutive snapshots of the snapshotupdates 304A-304B. The sliding window 306 indicates the active snapshotupdates 304B; that is, the six most recent snapshot updates of thedepicted example.

Data for the changing base dictionary 302 may reside in one physicalstorage device (e.g., a hard disk) or may reside on one or morepartitions distributed across multiple storage devices. As an examplethe changing base dictionary 302 may be a dictionary of block-levelstorage residing on one or more block-level storage devices of a blocklevel storage service provided by a computing resource service provider.The block-level storage devices may, for instance, be operationallyattached to virtual computer systems provided by a virtual computersystem service of the computing resource service provider to serve aslogical storage units (e.g., virtual drives) for the computer systems. Ablock-level storage device may enable the persistent storage of dataused/generated by a corresponding virtual computer system, whereas thevirtual computer system service may only provide ephemeral data storage.As discussed in more detail below a base dictionary 302 (and/or one ormore sub-dictionary) can change over time for various reasons. Forexample, changing a base dictionary 302 over time can make the basedictionary 302 more effective, efficient, compressive, or the like.

As shown in FIG. 3, the example 300 has a snapshot depth of six, andthus each of the snapshot updates 304A-304B can be seen to comprise atleast ⅙^(th) of the changing base dictionary 302. For example, thesnapshot update at time t₁ may include the first sixth of the basedictionary 302. Likewise, the snapshot update at time t₂ may include thesecond sixth of the base dictionary 302. The snapshot update at time t₂may also include any changes to the first, third, fourth, fifth, orsixth portions of the base dictionary 302 that have occurred since timet₁. Similarly, the snapshot update at time t₃, may include the thirdsixth of the dictionary 302, as well as any changes to the first,second, fourth, fifth, or sixth portions of the dictionary 302 that haveoccurred since time t₂.

This process may continue up to the snapshot update at time t₆, whichmay include the final sixth of the base dictionary 302, as well as anychanges to the first, second, third, fourth, and fifth portions of thebase dictionary 302 that have occurred since time t₅. Note that at thispoint in time, the combination of each of the snapshot updates t₁through t₆ covers the entire base dictionary 302. Note as well, that atthis point in time the sliding window 306 would comprise the snapshotsof time t₁ through t₆.

Note also that, the snapshot update captured at time t₇ once againcaptures the first sixth of the dictionary 302. This snapshot updatecaptured at time t₇ may also include any changes to the second, third,fourth, fifth, and sixth portions of the dictionary 302 that haveoccurred since time t₆. Because the snapshot update captured at time t₇may include at least the first portion of the dictionary 302, thesnapshot update captured at time t₁ may be redundant or obsolete. Insome implementations, the snapshot update captured at time t₁ cansubsequently be deleted to conserve space. Note that, in some of theseimplementations, these historical snapshot updates 304A (i.e., snapshotupdates outside the sliding window 306) are retained until a customerowner of the dictionary 302 orders their deletion, whereas in otherimplementations, these historical snapshot updates 304A are deletedautomatically once they are outside the sliding window 306.

In still other implementations, a certain number of most recenthistorical snapshot updates may be retained, or each historical snapshotupdates may be retained for a certain period of time (e.g., five days)before being deleted, or may be retained until the cumulative size ofthe historical snapshot updates 304 exceeds a certain threshold uponwhich time select historical snapshot updates may be deleted (e.g.,oldest first) to keep the space requirements for the historical snapshotupdates below the threshold. Thus, at time t₇ the sliding window 306would cover the snapshots of time t₂ through t₇.

The sliding window 306 is simply intended to illustrate the activesnapshot updates that comprise the full changing dictionary 302. Thesliding window 306 would normally comprise the most recent snapshotupdates up to the maximum snapshot depth, which in the example 300 wouldbe six, or up to the last full snapshot, whichever occurs first. Forexample, at time t₀ (not depicted), a full snapshot (i.e., a capture ofall data of the dictionary; also referred to as a base snapshot) mayhave been taken of the dictionary. In this example at time t₁, thesliding window may include the snapshot update captured at time t₁ plusthe full snapshot.

Similarly, the sliding window at time t₅ may include the snapshotupdates at time t₁ through time t₅ plus the full snapshot. However, whenthe snapshot update is captured at time t₆ all of the data of thedictionary 302, in its most up-to-date version, should be included inthe accumulated snapshot updates captured from time t₁ through t₆,rendering the full snapshot at time t₀ redundant or obsolete.

Thus, in the example 300 the most recent snapshot update was captured attime t₁₆, and, as illustrated, the sliding window 306 now includes thesnapshot updates captured from time t₁₁ through t₁₆. This sliding window306 also means that the snapshot updates captured from time t₁ throughtime t₁₀ (including, any full snapshots captured at that time such as attime t₀) should be redundant or obsolete, and in some implementationsare deleted.

Note additionally that a full snapshot can be constructed from theactive snapshot updates 304B. For example, at a time t₁₇ (not shown) afull snapshot may be assembled by first obtaining the oldest snapshotupdate of the active snapshot updates 304B (the snapshot update capturedat time t₁₁), then combining that snapshot with the next oldest snapshotupdate of the active snapshot updates 304B (the snapshot update capturedat time t₁₂), then combining with the next oldest snapshot update of theactive snapshot update 304B (the snapshot update captured at time t₁₃),and so on until finally combining the most recent snapshot update of theactive snapshot updates 304B (the snapshot update captured at time t₁₆).The dictionary 302 may be restored to the state it was in at a time ofits most recent snapshot update in a similar manner.

Note that there are various implementations that may be used to generatea full snapshot or obtain a current state of a dictionary from itsactive snapshot updates than the one described above. In the mannerdescribed above, by starting with the oldest of the active snapshotupdates data in an older snapshot that changed and the change capturedin a more recent snapshot, may be naturally overwritten by the updateddata. However, another technique may be to start with the most recentsnapshot update (e.g., the snapshot update captured at time t₁₆) andwork backwards to the oldest of the active snapshot updates, butskipping over any data in an older snapshot update that has already beenincluded in a more recent snapshot update.

Still another technique may be to generate a manifest that includes areference to every identifier and/or definition of the dictionary 302and the location where the most recent version of the identifier and/ordefinition can be found in the active snapshot updates 304B, and thengenerate a full snapshot (which may also be referred to as a fullre-base snapshot) by a selectively obtaining only the most recentversions of the identifier and/or definition from the particularsnapshot update(s) hosting them. Obtaining the current state of thedictionary 302 may be performed in a similar manner. Note as well, thata partial current state obtaining of a dictionary 302 may be performedby locating the identifier and/or definition to be restored within themanifest, and selectively obtaining the most recent versions ofidentifier and/or definition from their respective active snapshotupdates 304B.

In some implementations each of the snapshot updates 304A-304B have anassociated set of permissions that grants access (e.g., read access,write access, etc.) to that particular snapshot update, such that a useror other entity having a first set of permissions granting access tofirst snapshot update is unable to access a second snapshot updateunless the user or other entity also has a second set of permissionsgranting access to the second snapshot update. In some examples, one ormore of the snapshot updates 304A-304B share a set of permissions thatgrant access to the one or more of the snapshot updates 304A-304B. Inthis manner, network security may be improved because users and otherentities can be assigned permissions only to the actual snapshot theyneed to access.

FIG. 4 depicts a representation 400 of a dictionary 402 and an initialsnapshot 404 of an example of the present disclosure. The dictionary 402depicted in FIG. 4 is comprised of 25 chunks 408 of data, from chunk 1at position 1 to chunk 25 at position 25. For purposes of this example,each of the chunks 408 may include a portion of a dictionary or mayinclude one or more identifiers and/or definitions. The dictionary 402may be a dictionary similar to the dictionary 302 described inconjunction with FIG. 3. FIG. 4 also illustrates an initial snapshot 404at a time t₀. The initial snapshot 404 may be at first snapshot of thedictionary 402, may be a re-based snapshot (as described above inconjunction with FIG. 3), or any other full snapshot of the dictionary402. That is, each of the chunks 408 are included in the initialsnapshot 204 in a same version as they were in the dictionary 402 at thetime represented by time t₀. FIG. 4 represents an initial state of thedictionary 402 and the dictionary 302 of FIG. 3 prior to capturing anyof the snapshot updates depicted in FIG. 3.

Similar to FIG. 4, FIG. 5 depicts representations 500 of a dictionary asdata of the dictionary (e.g., dictionary portions, identifiers and/ordefinitions) changes and as snapshot updates 504A-504N are taken overtime. For example, dictionary 502A represents the dictionary at time t₁,dictionary 502B represents the dictionary at time t₂, dictionary 502Crepresents the dictionary at time t₃, and dictionary 502N represents thedictionary at time t₁₀. The dictionary may be a dictionary similar tothe dictionaries 108, 110, 112, 202, 204, 302, and 404 of FIGS. 1-4respectively. The representations 500 depict an example of the presentdisclosure with a maximum snapshot depth of 10; in other words, a fullsnapshot or a full restore of the dictionary may be generated using nomore than 10 consecutive snapshot updates of the present disclosure.

Starting at time t₁, it is seen that chunks 5, 11, and 20 have changedsince an initial state (e.g., a state of the dictionary at time t₀ asdepicted in FIG. 4). As part of the first snapshot update, these changedchunks may naturally be included in the incremental portion of the firstsnapshot update 504A. Additionally, at time t₁ a proportion of theentire dictionary may also be included in the first snapshot update504A, the proportion being based at least in part on the maximumsnapshot depth, which in the case of the representations 500 would be1/10 or 10%. This may be achieved, for example, by incrementing asnapshot counter, taking the modulus of the snapshot depth (being 10, inthat example) of an identifier or order number in the manifest for eachchunk in the manifest, and including the chunks whose modulus 10 matchesthe modulus 10 of the snapshot counter. In other words, at time t₁ thesnapshot counter may be 1, and 1 mod 10 is 1.

Assuming the numbers of the chunks in the dictionary 502A correspond toidentifiers for the particular chunks, the modulus of the identifier forchunk 1 of the dictionary 502A, 1 mod 10 is 1, which matches the modulusof the snapshot counter, and therefore chunk 1 would be included in theproportional portion of the first snapshot update. However, the modulusfor chunk 2 of dictionary 502A, 2 mod 10 is 2, which does not match themodulus 10 of the snapshot counter, therefore chunk 2 would be excludedfrom the proportional portion of the first snapshot update, and so on.

Skipping down, however, the modulus for chunk 11 a dictionary 502A, 11mod 10 is 1, which again matches the modulus 10 of the snapshot counterso chunk 11 would normally be included in the proportional portion ofthe first snapshot update. Chunk 21 is included for the same reason. Theblack arrows in the snapshot updates 504A-04N are intended to highlightthe chunks corresponding to the proportional portion. Note though, thatchunk 11 has also been modified since the initial state, as indicated bythe superscript of the snapshot counter (¹). Thus, chunk 11 would havebeen already included in the incremental portion of the first snapshotupdate.

Although examples in the present disclosure describe determining whichchunks (or sets of identifiers and/or definitions) to include in theproportional portion based at least in part on a modulus of some valueassociated with the chunk (or one or more identifiers and/ordefinitions), such as an identifier or counter, other methods arecontemplated as well. For example, at a first time, a first 1/Nth ofchunks in the dictionary may be included in the proportional portion,where N is the snapshot depth, and at a second time the next 1/Nth ofchunks (or one or more identifiers and definitions) in the dictionarymay be included in the proportional portion, and so on. This maycontinue until, after including the last 1/Nth, the next snapshot updateincludes the first 1/Nth of chunks (or one or more identifiers and/ordefinitions) again, and so on.

An alternative may be to base the snapshot depth on time. For example,the proportional portion may include as many chunks (or one or moreidentifiers and/or definitions) as can be copied to the snapshotlocation within a certain period of time (e.g., 1 minute, 5 minutes, 60minutes, one day, one week, one month, etc.). The certain amount of timemay be based at least in part on the frequency that snapshot updates arebeing performed. For example, if snapshot updates are performed (e.g.,by instruction from a customer owner) on the dictionary every 5 minutes,the proportional portion may include only as many chunks as can becopied within 2 minutes, in order to provide enough time to copy theincremental portion before the next snapshot update is performed.

In some implementations, the version of chunk 11 included in theproportional portion of the first snapshot update would be the previousversion (i.e., from the initial snapshot at t₀); that is, the firstsnapshot update would include both the previous version of chunk 11 andthe current version of chunk 11. In some implementations, theincremental portion of the snapshot update is determined before theproportional portion. In other implementations, the proportional portionof the snapshot update is determined before the incremental portion. Ineither implementation, a duplicate of a chunk that has already beenincluded in a portion of the snapshot update may be excluded to avoidduplication. That is, in these implementations the set of dictionaryportions or the set of identifiers and corresponding definitions in theincremental portion and the set of dictionary portions or the set ofidentifiers and corresponding definitions in the proportional portionmay be disjoint from each other (i.e., they do not share the sameidentifiers and corresponding definitions or do not share the samedictionary portions).

However, in other implementations, such as where each portion of thesnapshot update are generated and stored separately but in associationwith each other, duplicate chunks may be retained. In other words, inthese other implementations, the set of dictionary portions or the setof identifiers and corresponding definitions in the incremental portion,and the set of dictionary portions or the set of identifiers andcorresponding definitions in the proportional portion may intersect attimes. Thus, as depicted in the representations 500, chunks 1, 5, 11,20, and 21 may be included in the incremental and proportional portionsof the first snapshot update 504A.

Moving on to the dictionary 502B at time t₂, it can be seen that noupdates have occurred to any chunks between time t₁ and time t₂. Thus,the second snapshot update 304B only includes a proportional portion(indicated by the black arrows). That is, the snapshot counter has beenincremented to two, meaning that the modulus 10 of chunks 2, 12, and 22matches the modulus 10 of the snapshot counter, and thus chunks 2, 12,and 22 will be included in the second snapshot update at time t₂.Snapshot window 510A is intended to illustrate the chunks collectivelystored in the first snapshot update and the second snapshot update.

Proceeding to time t₃, it can be seen that chunk 2 has changed betweentime t₂ and time t₃, as indicated by the superscript of the snapshotcounter (³), as well as chunks 19 and 20. Thus, chunks 2, 19, and 20will be included in the incremental portion of the third snapshotupdate, and chunks 3, 13, and 23 will be included in the proportionalportion (indicated by the black arrows) of the third snapshot updatebecause the modulus 10 of the identifiers of these chunks match themodulus 10 of the snapshot counter. Note that chunks 2 and 20 havealready been included in prior snapshot updates (i.e., the secondsnapshot update and the first snapshot update respectively). Becausechunks 2 and 20 in the third snapshot update reflect the most recentchange to those respective chunks, during a re-base or during a restoreof a dictionary from the snapshot the older versions of these respectivechunks (i.e., from the second snapshot update and the first snapshotupdate) may be omitted from the restore, or, alternatively, may beoverwritten by the more recent version of those respective chunks in thethird snapshot update.

In still other implementations, the older versions of respective chunksare deleted from their respective snapshot updates (i.e., the secondsnapshot update and the first snapshot update). In even otherimplementations, the versions of chunks 2 and 20 included in theproportional portion of the first snapshot update would be the previousversions (i.e., chunk 2 from the initial snapshot at t₀ and chunk 20from the first snapshot update at t₁); that is, the third snapshotupdate would include both the previous version of chunks 2 and 20 andthe current versions of chunks 2 and 20. Snapshot window 510Bconsequently illustrates how, with each succeeding snapshot update, thesnapshot updates collectively store more of the state of the dictionary502C.

The process may continue for each snapshot update as described abovesuch that, at time t₁₀, it can be seen that, for the dictionary 502N,chunk 5 was last modified prior to time chunks 2 and 20 were lastmodified between time t₂ and t₃, chunk 14 was last modified between timet₃ and t₄, chunks 7 and 16 were last modified between time t₄ and t₅,chunks 6 and 12 were last modified between time t₅ and t₆, chunks 8 and22 were last modified between time t₆ and t₇, chunks 13 and 15 were lastmodified between time t₇ and t₈, and chunks 9, 10, 21, and 25 were lastmodified between time t₉ and t₁₀. It can also be seen that chunks 1, 3,4, 17, 18, 23, and 24 have not changed at all since the initialsnapshot. Thus, at this time it is seen that chunks 9, 10, 21 and 25would be included in the incremental portion of the tenth snapshotupdate 504N, and chunks 10 and 20 would be included in the proportionalportion of the tenth snapshot update 504N (with duplicate chunk 10discarded or not discarded from one of the portions, or previous versionof chunk 10 included in the proportional portion, depending on theimplementation).

Note that chunk 20, which would be included in the proportional portionof the 10^(th) snapshot update 504N has not changed since time t₃, andthus was already included in the third snapshot update, which is stillwithin the current snapshot window. Consequently, in someimplementations, chunk 20 can be excluded from the 10^(th) snapshotupdate because, during a full re-base or when obtaining the currentstate of the dictionary 502N, the most recent version of chunk 20 canstill be obtained from a previous snapshot (i.e., the third snapshotupdate) within the current snapshot window. Furthermore, it can be seennow that, because the snapshot window 510M now includes as many snapshotupdates as the maximum snapshot depth of 10, the totality of all of theactive snapshot updates 504A-504N in the snapshot window include all ofthe chunks required for a full re-base or a full restore of the state ofthe dictionary 502N at time t₁₀.

In some implementations, snapshot updates can be performed on-demand,such as in response to a request from a dictionary administrator orother entity authorized to request a snapshot of the dictionary. Inother additional or alternative implementations, snapshot updates occurin response to a particular event. For example, a snapshot update may betriggered to occur after every 1,000 writes to the dictionary beingsnapshotted. As another example, a snapshot update may be triggered tooccur when a defined number of changes and/or additions have been madeto the dictionary portions or identifiers and/or definitions of thedictionary.

In another additional or alternative implementation, a snapshot updatethat is scheduled or instructed to be performed can be postponed uponthe occurrence of a particular event and resumed upon the occurrence ofanother event. For example, if a computing device hosting the dictionarydetects that an operating temperature has exceeded a thresholdtemperature, a schedule snapshot update may be postponed until theoperating temperature is detected to have dropped below the thresholdtemperature.

FIG. 6 illustrates a representation 600 of an example of the presentdisclosure. Specifically, FIG. 6 depicts making snapshot updates inaccordance with an example of the present disclosure of a dictionary 602divided into six data portions, where each data portion may comprise oneor more dictionary portions or one or more identifiers and/orcorresponding definitions. The representation 600 depicts the dictionary602 and five snapshot updates 604A-604E, where each snapshot updateincludes a proportional portion 612A-612E and an incremental portion614A-614E. The maximum snapshot depth of the example depicted in FIG. 6is three, represented by the snapshot window 606 showing the three mostrecent snapshot updates 604C-604E as the active snapshots.

At time t₁, a first full manifest may be created. The manifest indicateslocations where data portions may be found, such that the manifest canact as a map to the versions of data portions at time t₁. At time t₁,since no previous snapshot updates exist, the locations of the dataportions will likely all be from the dictionary 602 or an initialsnapshot at time t₀ (not shown). As can be seen, at time t₁ (snapshotcount=1), data portions 1 and 4 are included in the first proportionalportion 612A (modulus 3 of the snapshot count equals modulus 3 of 1 and4), and data portions 3 and 5 have been modified since the initialsnapshot at time t₀ and are therefore included in the first incrementalportion 614A of the first snapshot update 604A. A first partial manifest(also referred to as a “change set”) may be generated for the firstsnapshot update 604A to reflect the data portions that are included inthe first snapshot update 604A; alternatively the first full manifestmay be updated to reflect these locations. These manifests may be storedin association with the first snapshot update 604A (e.g., in a samedirectory or in a database record having information indicating thestorage location of the first snapshot update 604A).

At time t₂, a second full manifest may be created. The second fullmanifest may indicate that the most recent version of data portions 1and 5 are located in the first snapshot update 604A, with the rest beinglocated on the dictionary 602 or in the initial snapshot at time t₀.Thus, at time t₂ (snapshot count=2), data portions 2 and 5 are includedin the second proportional portion 612B (modulus 3 of the snapshot countequals modulus 3 of 2 and 5). With a snapshot depth of three, the firstand second snapshot updates 604A-604B are within the sliding window 606at this time, and it can be seen that data portion 5 is included in bothsnapshots.

In some examples, data portion 5 is removed from the first snapshotupdate 604A to conserve space, in other examples data portion 5 isomitted from the second snapshot update 604B to conserve space (however,care must be taken to ensure that data portion 5 is carried forward asthe sliding window 606 passes the first snapshot update 604A), and instill other examples data portion 5 is retained in both the first andsecond snapshot updates 604A-604B. It can be seen that data portions 3and 4 have changed since time t₁, and therefore will be included in thesecond incremental portion 614B of the second snapshot update 604B. Asecond partial manifest may be generated for the second snapshot update604B to reflect the data portions that are included in the secondsnapshot update 604B; alternatively, the second full manifest may beupdated to reflect these locations. These manifests may be stored inassociation with the second snapshot update 604B.

At time t₃, a third full manifest may be created indicating that themost recent version of data portion 1 is still in the first snapshotupdate 604A, most recent versions of data portions 3 and 4 are in thesecond snapshot update 604B, and the most recent version of data portion6 is still on the dictionary 602 or in the initial snapshot at time t₀.At time t₃ (snapshot count=3), data portions 3 and 6 are included in thethird proportional portion 612C. Note that, depending on the particularimplementation, the data portion 3 may be obtained from the secondsnapshot update 604B, the dictionary 602, or omitted from the thirdproportional portion 612C since it is currently included in the secondsnapshot update 604B which is still inside the sliding window 606.

It can be seen that data portions 2 and 5 have changed since time t₂,and therefore will be included in the third incremental portion 614C ofthe third snapshot update 604C. Note that, at this point, due to themaximum snapshot depth being three, the sliding window 606 now no longerincludes the initial snapshot at time t₀. In some implementations, thefull initial snapshot at time t₀ can be deleted, as the most currentversions of the data portions should be found within the sliding window606. A third partial manifest may be generated or the third fullmanifest may be updated in a similar manner as described above.

In a similar manner, at time t₄ the fourth proportional portion 612D ofthe fourth snapshot update 604D will include data portions 1 and 4. Notethat because the initial snapshot at time t₀ is no longer included inthe snapshot window 606, data portion 1 may be retrieved from the firstsnapshot update 604A. In alternate examples, rather than retrieving dataportion 1 from snapshot update 604A, data portion 1 is obtained directlyfrom the dictionary. In these examples, obtaining the proportionalportion directly from the dictionary may be preferable in order toreduce error propagation. For example, if data corruption occurredduring a copy operation from an earlier snapshot, that data corruptionmight be inadvertently copied into future snapshot updates.

However, by obtaining the proportional portion directly from thedictionary, the snapshot update will at least have the proportionalportion in the state it is on the dictionary. Note however, obtainingthe proportional portion directly from the dictionary may be more taxingon the resources of the computing system hosting the dictionary. In someimplementations, the proportional portion can alternate obtaining theproportional portion from a previous snapshot and obtaining theproportional portion from the dictionary (i.e., redundant copy)according to a schedule or according to resource demand. For example, adaily proportional portion may be obtained from a previous snapshotSunday through Friday, but every Saturday it is obtained directly fromthe dictionary (in this manner data may be periodically refreshed). Onthe other hand, in another example, proportional portion may be obtainedfrom directly from the dictionary unless resource usage/demand for thedictionary exceeds a threshold, whereupon the proportional portion maybe obtained from a previous snapshot instead.

Note that in examples of the present disclosure, data portions areobtained from the dictionary by an administrator of the dictionarycausing the data portions to be pushed to the system storing thesnapshots, such as through an application executing in a virtual machineinstance attached to the dictionary or otherwise by an instructionthrough an application programming interface. Alternatively, in someimplementations, the system performing the snapshotting process of thepresent disclosure accesses the dictionary on its own and copies thedata portions directly from the dictionary.

As for the fourth incremental portion 614D, it is seen that dataportions 2, 4, and 5 have changed since time t₃, and therefore theversions of those data portions will be retrieved from the actualdictionary 602. Note however, that in this example, the fourthproportional portion 612D includes the previous version of data portion4 while the fourth incremental portion 614D includes the current versionof data portion 4. This can be desirable for performing a rollback in amanner described below. However, it should be noted that not allexamples of the present disclosure retain both versions in the fourthsnapshot update 604D. At this point, the sliding window 606 includes thesecond, third, and fourth snapshot updates 604B-604D. A fourth partialmanifest may be generated or the fourth full manifest may be updated ina similar manner as described above.

The techniques for the fifth snapshot update 604E can follow a similarpattern. At t₅ (snapshot count=5), the fifth proportional portion 612Eincludes data portions 2 and 5, and it can be seen that data portion 1has changed since time t₄ and therefore will be included in the fifthincremental portion 614E. At this time the sliding window 606 will be atthe location depicted in FIG. 6, and the active snapshot updates are thethird, fourth, and fifth snapshot updates 604C-604E. A fifth partialmanifest may be generated or the fifth full manifest may be updated in asimilar manner as described above.

In the example depicted in FIG. 6, it may be possible to rollback to anyprevious point in the sliding window 606. For example, in a case whereit is desirable to obtain the state of the dictionary at time t₃, amanifest may first be generated to determine the locations of the dataportions in the state they would have been at time t₃. In some examples,this is performed by first examining the manifest that was generated attime t₃ for the locations of the data portions. For example, themanifest for the third snapshot update 604C would indicate that thesecond, third, fifth, and sixth data portions can be found at locationsin the third snapshot update 604C, that first data portion may be foundin the first snapshot update 604A, and that the fourth data portion maybe found in the second snapshot update 604B. However, since the firstand second snapshot updates 604A-604B are no longer in the slidingwindow 606, they may be unavailable.

Therefore, the system performing the rollback process may look at themanifests of succeeding snapshot updates 604D-604E to locate dataportions 1 and 4. As can be seen, the data portion 1 and 4 are found inthe fourth snapshot update 604D. However, data portion 4, as noted,changed between times t₃ and t₄. Because restoring data portion 4 fromthe fourth incremental portion 614D would result in a version of dataportion 4 that was not present in the dictionary at time t₃, the dataportion 4 from the fourth proportional portion 612D, which reflects theversion of data portion 4 as it was at time t₃.

In this manner, a rollback of the dictionary 602 may be performed forany time within the sliding window 606. Note that in some examples, theproportional portion of data portion 4 would not be carried forward tothe snapshot update 604D; in such examples, data portion 4 may beobtained from a previous snapshot update (e.g., snapshot update 604B)outside the sliding window 606. In such examples, historical snapshotupdates 604A-604B might not be automatically deleted or may be retainedat least temporarily in order to provide the ability to roll back to aprevious state.

FIG. 7 is a block diagram illustrating an example of a process 700 forperforming a snapshot update in accordance with various examples. Theprocess 700 may be performed by any suitable system such as a server102, 804, 904, 1004 of FIGS. 1, 8, 9, and 10, multiple computing devicesin a distributed system of a computing resource service provider, or anyelectronic client device such as the user device 104, 802, 902, 1002 ofFIGS. 1, 8, 9, and 10. The process 700 includes a series of operationswherein a snapshot is obtained, a dictionary manifest generated, asnapshot count is incremented, and snapshot updates of the dictionaryare determined, obtained, and stored.

In 702, a maximum snapshot depth for a dictionary is obtained. Forexample, a service provider may determine that no more than 100 snapshotupdates should be active (i.e., within the current snapshot window), andconsequently set the maximum snapshot depth to 100. In someimplementations, the determination of the maximum snapshot depth is madeon a dictionary-by-dictionary basis. For example, small dictionaries maybe configured to have a larger snapshot depth (e.g., 1,000 snapshotupdates), whereas large dictionaries may have smaller snapshot depths(e.g., 100), because more storage resources may be required for storingthe snapshot updates of the larger dictionaries than the smallerdictionaries.

Similarly, performance concerns may dictate the maximum snapshot depth.For example, for a given dictionary size, the shallower the snapshotdepth, the longer it will take to generate the snapshot update. Taking a1.6 gigabyte (GB) dictionary as an example, a snapshot depth of 16 meansthat each snapshot update will be at least 10 megabytes (MB) in size,whereas a snapshot depth of 6 means that each snapshot update will be atleast 100 MB in size, and consequently consume more time and resourceswhile being generated than the smaller snapshot.

In some implementations, the maximum snapshot depth can be specified bya customer of a computing resource service provider, where the computingresource service provider provides the dictionary to the customer. Forexample, the computing resource service provider may provide anapplication programming interface to the customer through which thecustomer can specify the customer desired maximum snapshot depth for theparticular customer dictionary. Alternatively, a dictionaryadministrator can specify a maximum snapshot depth.

In 704, the system performing the process 700 may obtain a manifest thatcontains locations of data portions of a dictionary (also referred to as“chunks”). The locations of the data portions indicated in the manifestmay be locations in one or more full or snapshot updates, or may belocations of the data portions in the actual dictionary (e.g., locationsof identifiers and/or definitions). For example, in a scenario where afull snapshot exists for a dictionary as well as five snapshot updatesof the present disclosure, the manifest might indicate that a mostrecent version of first chunk is located at a particular location in thefull snapshot, a most recent version of second chunk is located in aparticular location in a third snapshot update, a most recent version ofthe third chunk is located in a particular location in a first snapshotupdate, and so on. The manifest may also indicate the locations of thechunk in the actual dictionary so that it can be determined whether thechunk in the actual dictionary is more up-to-date than (i.e., has beenupdated since) the most recent version of the corresponding chunk in apartial or full snapshot.

In 706, a snapshot count is incremented. In examples, the systemperforming the process 700 keep track of the number of snapshot updatesmade of a particular dictionary by use of the snapshot count. Thesnapshot count is incremented in 706 to reflect the upcoming snapshotupdate generated in 708-14. In 708, an incremental snapshot isgenerated. The incremental snapshot includes data portions that havebeen modified since the preceding snapshot update was made.

For example, if one or more identifiers and/or corresponding definitionsof a data portion was modified before time t₁ and the data portion wasincluded in a snapshot update taken at time t₁, if, at time t₂, none ofthe identifiers and/or definitions of the data portion had been modifiedsince time t₁, the data portion would not be included in the incrementalsnapshot taken at time t₂. On the other hand, if one or more identifiersand/or corresponding definitions of the data portion had been modifiedbetween time t₁ and time t₂, the data portion would be included in theincremental snapshot taken at time t₂. Similarly, any data portion whoseidentifiers and/or definitions remain unmodified from an initialsnapshot or from the dictionary at an initial state would not beincluded in the incremental snapshot.

Note that in some implementations, the operations of 608, rather thangenerating an actual snapshot, generate a list of data portions thathave been modified since the preceding snapshot and their locations inthe dictionary to be included in the snapshot update. That is, in someexamples the operations of 708-10 result in a set of identifiers and/ordefinitions to be included in a snapshot update, and the operations of712 may generate the snapshot update based at least in part on that setof identifiers and/or definitions.

In 710, the system performing the process 700 may determine a set ofidentifiers and/or definitions to include in a proportional portion ofthe snapshot update. The set of identifiers and/or definitions maycomprise at least 1/Nth of the identifiers and/or definitions of thedictionary, where N is the maximum snapshot depth. The selection ofwhich 1/Nth of the identifiers and/or definitions to include in the setof identifiers and/or definitions may be made in a variety of ways. Forexample, where N is 10, the first proportional portion (i.e., theproportional portion determined by the system performing the process 700at a time t₁) may be the first 10% of identifiers and/or definitions inthe dictionary, the second proportional portion (i.e., the proportionalportion determined by the system performing the process 700 at a timet₂) may be the second 10% of identifiers and/or definitions in thedictionary, and so on.

Alternatively, where N is 10, the dictionary may be divided intonumbered chunks, and if the modulus 10 of the chunk number matches themodulus 10 of the incremented snapshot count, that corresponding chunkmay be included in the set of identifiers and/or definitions for aproportional portion of the snapshot update. The latter method mayresult in the proportional portions being selected in aninterlaced/interleaved fashion, while the former method may result inthe proportional portions being selected in a progressive (i.e.,non-interlaced) fashion. There may be advantages of one method over theother, depending on the particular implementation of the presentdisclosure, and other methods for selecting proportional portions areadditionally contemplated.

In some examples, the maximum snapshot depth (i.e., the size of thesliding window) is dynamically adjusted. For example, the maximumsnapshot depth may be increased during periods of scarce computingresources in order to accommodate smaller snapshot updates. Conversely,during periods of surplus computing resources (e.g., network demandfalls below a minimum threshold/sentinel value, a number of idle storagedevices exceed an upper threshold, processor idle time exceeds athreshold, etc.), the maximum snapshot depth may be decreased, allowingfor larger snapshot updates. Note that, in some cases where the maximumsnapshot depth is dynamically decreased, the deletion of some snapshotupdates outside the sliding window may be delayed until all parts of thedictionary/rolling rebase have been carried forward into the slidingwindow.

Alternatively, if it is estimated/determined that the time required toperform the process 700 at a current maximum snapshot depth would exceeda maximum time threshold, the maximum snapshot depth may be increased toan amount sufficient to keep the time required to perform the process700 below the threshold. Determinations of whether computing resourcesare scarce or in surplus may be made by a monitoring application orservice that may be configured to adjust the maximum snapshot depth to adetermined appropriate depth dynamically. For example, if computingresources are determined to be sufficient (e.g., little or noperformance impact to customers of the computing resource serviceprovider) to perform a full snapshot, the maximum snapshot depth may bechanged to 1 for as long as available computing resources are determinedto be sufficient, thereby causing full snapshots to be performedperiodically or otherwise according to the snapshot update schedule.

As another example, if a snapshot update is being performed with amaximum snapshot depth of 10 and it is determined in 710-12 by thesystem performing the process 700 that computing resources currentlyallocated to performing the process 700 need to be released and madeavailable to some other process, the maximum snapshot depth may bedynamically increased in order for the process 700 to complete morequickly. For example, if, in the previous example, the system performingthe process had up to this point only determined and obtained 1% of theproportional portion of the snapshot update, the maximum snapshot depthmay be increased to 100, and the process 700 may consequently beconcluded. In this manner, in such examples, the number of data portionsin the set of data portions and/or sizes of the proportional snapshotscan vary from snapshot to snapshot.

In another example, the maximum snapshot depth is adjusted on demand bya customer owner of the dictionary or some other authorized entity suchas a dictionary administrator. For example, a computing resource serviceprovider may have a billing plan whereby customers are charged based atleast in part on the number of dictionary snapshots performed. In suchan example, a customer may choose to reduce the maximum snapshot depthin order to minimize his charges. As another example, a computingresource service provider may have a billing plan whereby customers arecharged based at least in part on the size of snapshots that areperformed. In such an example, a customer may choose to increase themaximum snapshot depth in order to reduce the size of the snapshotupdates and thereby minimize his charges. The maximum snapshot depth maybe adjusted in these examples using a web interface and/or anapplication programming interface provided by the computing resourceservice provider.

Also in 710, in some examples, data portions in the set of identifiersand/or definitions which are duplicative of identifiers and/ordefinitions already selected for the incremental portion of 708 areexcluded from the set of identifiers and/or definitions. In this manner,the size of the snapshot update may be minimized by avoiding theinclusion of duplicate identifiers and/or definitions. Note that inexamples where the order of determining the identifiers and/ordefinitions for the incremental portion and the identifiers and/ordefinitions for the proportional portion is reversed, the duplicate dataportions may be excluded from the incremental portion instead.

Additionally, in some implementations where a most recent version ofidentifiers and/or definitions is selected for the set of identifiersand/or definitions for the proportional portion is found in a snapshotwithin N snapshots of the current snapshot (i.e., the snapshot window),that identifier and/or definition would also be excluded from the set ofidentifiers and/or definitions. That is, where a goal of an example ofthe present disclosure is to ensure that a full re-base or restore ofthe dictionary can be accomplished using only N snapshots, as long asthat identifier and/or definition is within the snapshot window the goalcan be accomplished and the size of the current snapshot update can beminimized by excluding the duplicate identifier and/or definition.

As noted, in some implementations, the snapshots of 708 and 712 can becombined into a single snapshot update, whereas in other implementationsthe snapshots of 708 and 712 can result in separate snapshots that maybe both stored in association with the snapshot count number and may becumulatively considered to be the snapshot update.

Note that the process 700 may be performed periodically (e.g., everyhour, every day, every week, etc.) or according to some other schedule(e.g., next Wednesday at 3:00 PM, every third Tuesday, the last fullweekend in July, etc.). Additionally or alternatively, the process 700may be performed in response to the occurrence of an event. For example,the process 700 may be triggered by the system detecting that computingresource usage, such as network demand, has fallen below a thresholdvalue, making it a good time to perform the process 700.

As another example, the system may detect that a number of changedidentifiers and/or definitions have exceeded the threshold, andtherefore the process 700 should be performed to capture those changes.Similarly, as another example, the system may detect that a identifierand/or definition or other data portion that has been flagged with highimportance has changed, and consequently the process 700 should beperformed to capture that change. Additionally or alternatively, theprocess 700 may be performed on demand in response to a request by acustomer owner of the dictionary or some other authorized entity toperform a snapshot such as a dictionary administrator. Note too that oneor more of the operations performed in 702-714 may be performed invarious orders and combinations, including in parallel. For example, insome examples, the operations of 710-712 are performed prior to or inparallel with the operations of 708.

In various examples, snapshots as discussed in FIGS. 3-7 can be a set ofdictionaries 101, 200 as discussed in FIGS. 1 and 2, or the like. Forexample, referring to FIG. 1, one or more snapshot can be generated bythe server 102 to capture changes to a base dictionary 108 (and/orprimary or secondary sub-dictionaries 110, 112) and such snapshots canbe sent to the user device 104 so that a current state of the basedictionary 108 (and/or primary or secondary sub-dictionaries 110, 112)can be obtained at the user device 104 such that identifiers anddefinitions are shared between the server 102 and user device 104.

In one example, such snapshots can be used to generate at the userdevice 104 a set of one or more dictionaries that mirror a set of one ormore dictionaries at the server 102. In another example, such snapshotscan be used to obtain at the user device 104 a set of identifiers andcorresponding definitions that mirrors a set of one or more identifiersand corresponding definitions at the server 102. In other words, a setof dictionaries on the server 102 and user device 104 may not beidentical, but the set of identifiers and corresponding definitionsdefined by such sets can be identical.

Dictionaries can be used to encode and compress various types ofcommunications, including the communication of content such as webpages,videos, images, text, audio, and the like. In various examples, webpagecontent having a conventional form (e.g., HTML, JavaScript, CSS, images,and the like) can be compressed and presented as an image that mimicsthe webpage content. In some examples, such an image can be lossy. Inother words, the image of the content is not a one-to-one representationand may include less functionality, resolution, content, or the like,but may generally function and look the same way as the original contentwas intended to be presented.

Additionally, different dictionary sets can be used to encode differentportions of content. For example, where the content is a webpage, afirst set of dictionaries can be used for JavaScript, a second set ofdictionaries can be used for CSS, and a third set of dictionaries can beused for HTML. Accordingly, different dictionaries can be configured forcompressing a specific type of software code or a specific type ofcontent.

FIG. 8 illustrates one example set of communications 800 between a userdevice 802, compression servicer 804 and content server 806. The userdevice 802 can be the user device 104, 902, 1002 of FIG. 1, 9, or 10.The compression server 804 and/or content server 806 can be the server102, 904, 1004, of FIG. 1, 9, or 10. The communications 800 begin whereone or more content request is sent 808 to the compression server 804and one or more content request is sent 810 to the content server 806.For example, the user device 802 may request a webpage, which may alsoinclude images, video, audio, and the like, and this request may berouted through the compression server 804, which queries the contentserver 806, which stores the requested webpage content.

The content server 806 sends 812 content data to the compression server804, where a content image is generated 814 using a dictionary set. Forexample, as discussed herein, a dictionary set can comprise a basedictionary, one or more sub-dictionary, and/or one or more snapshotdictionary. The content image data is sent 816 to the user device 802,where the content image is presented 818 using the shared dictionaryset. For example, as discussed herein, the compression server 804 anduser device 802 can share a set of dictionaries (or identifiers andassociated definitions), and where the compression server 804 uses ashared dictionary set to generate 814 the content image, the user device802 can decode the content image data because it has access to the setof dictionaries (or identifiers and associated definitions).

Negotiating a set of one or more dictionaries to use to encode andcompress communications can be done in various suitable ways. Forexample, FIG. 9 illustrates a set of communications 900 between a userdevice 902 and server 904 for requesting content and presenting thecontent at the user device 902 using a selected dictionary set. The userdevice 902 can be the user device 104, 802, 1002 of FIG. 1, 8, or 10.The server 904 can be the server 102, 804, 806, 1004 of FIG. 1, 8, or10.

The communications 900 begin where a content request is sent 906 to theserver 904 and one or more identifiers of available dictionaries is sent908 to the server 904. In various examples, the content request caninclude a request for content such as a webpage, text, audio data, animage, a video, or the like. Dictionary identifiers or metadata caninclude an identifier of one or more dictionaries, including one or morebase dictionary, one or more sub-dictionary, and/or one or more snapshotdictionary, and the like). Dictionary identifiers can include unique ornon-unique identifiers of dictionaries, and can also include referenceto dependence among dictionaries, where applicable. In some examples,dictionary identifiers can include an identifier of identifiers presentin the dictionaries. In further examples, dictionary identifiers caninclude a version number, a date, a timestamp, or the like.

Returning to the communications 900, the server 904 selects 910 the bestavailable device dictionary set to handle the content request andcompresses 912 the content via the selected dictionary set. Accordingly,the selected 910 device dictionary set to handle the content request canbe a set of dictionaries that are shared by the user device 902 andserver 904 or a set of identifiers and definitions that are shared bythe user device 902 and server 904, even if the dictionaries that definethe shared identifiers and definitions are not identical.

Selecting 910 the best available device dictionary set to handle thecontent request can be based at least in part on various factorsincluding, dictionaries available to the server, 904 amount ofcompression gained, type of content being compressed, memory availableat the user device 902, geographic location of the user device 902,central processing unit (CPU) speed or capacity of the user device 902,type of user device 902, network conditions, internet service provider(IPS) handling the request, security associated with the request,throughput of the network, type of network, and the like.

Compressing 912 the content via the selected dictionary set canincluding encoding the content by identifying portions of the content,or code that defines the content, that matches definitions of theselected dictionary set and replacing these matching portions withappropriate identifiers associated with the identified portions of thecontent. Accordingly, the size of the content can be reduced, which canbe desirable when communicating such content over a network.

Returning to the communications 900, compressed content data is sent 914to the user device 902 where the content data is decoded using theselected dictionary set and the content is presented 918 at the userdevice. Decoding the content data can include identifying the selecteddictionary set and identifying identifiers in the content datacorresponding to identifiers in the dictionary set and replacing theidentified identifiers with definitions corresponding to the identifiersas defined by the dictionary set. Identifying the dictionary set can bebased at least in part on a communication from the server 904, which maybe a portion of the compressed content data. For example, the contentdata can include a header (e.g., IP header, HTTP header, or the like)that defines the dictionary set being used in the payload of the messageor the server and user device can negotiate use of a dictionary setduring a communication session such that packet headers need not includean indication of the dictionary set being used to compress the payloadof the packets during the session.

In the example of FIG. 9, the server 904 identifies and uses a set ofdictionaries (or a set of identifiers and definitions) that the userdevice 902 already has. However, in some examples, and as illustrated inFIG. 10, a server 1004 can identify one or more dictionaries that can besent to a user device 1002, which can be used to replace or augmentdictionaries present on the user device 1002. For example, FIG. 10illustrates a set of communications 1000 between a user device 1002 andserver 1004 for requesting content and presenting the content at theuser device 1002 using a selected dictionary set that includesdictionary portions that are sent to the user device 1002. The userdevice 1002 can be the user device 104, 802, 902 of FIG. 1, 8, or 9. Theserver 904 can be the server 102, 804, 806, 904 of FIG. 1, 8, or 9.

The communications 1000 begin where a content request is sent 1006 tothe server 1004 and one or more identifiers of available dictionariesare sent 1008 to the server 1004. As discussed above, the contentrequest can include a request for content such as a webpage, text, audiodata, an image, a video, or the like. Dictionary identifiers or metadatacan include an identifier of one or more dictionaries, including one ormore base dictionary, one or more sub-dictionary, and/or one or moresnapshot dictionary, and the like. Dictionary identifiers can includeunique or non-unique identifiers of dictionaries, and can also includereference to dependence among dictionaries, where applicable. In someexamples, dictionary identifiers can include an identifier ofidentifiers present in the dictionaries. In further examples, dictionaryidentifiers can include a version number, a date, a timestamp, or thelike.

Returning to the communications 1000, the server 1004 selects 1010 thebest available dictionary set to handle the content request andcompresses 1012 the content via the selected dictionary set.Accordingly, the selected 1010 dictionary set to handle the contentrequest can be a set of dictionaries (or a set of identifiers anddefinitions) that are present at the server 1004 and which may or maynot be present at the user device 1002.

Selecting 1010 the best available device dictionary set to handle thecontent request can be based at least in part on various factorsincluding dictionaries available to the server 1004 and/or user device1002, amount of compression gained, type of content being compressed,memory available at the user device 1002, geographic location of theuser device 1002, central processing unit (CPU) speed or capacity of theuser device, type of user device 1002, network conditions, internetservice provider (IPS) handling the request, security associated withthe request, throughput of the network, type of network, and the like.

Additionally, where one or more dictionaries are identified as beingdesirable for use in handling the content request, but such dictionariesare not currently available to the user device 1002, further factors canbe used to determine whether such candidate dictionaries should be usedto handle the request. For example, such further factors can include,the size(s) of the one or more dictionaries, time required to providethe one or more dictionaries to the user device 1002, time required toimplement the one or more dictionaries at the user device 1002, and thelike.

Accordingly, a determination can be made whether benefits in speed andcompression gained by such dictionaries would be outweighed by the timeit would take to send such one or more new dictionaries to the userdevice 1002 and implement the one or more dictionaries at the userdevice 1002. In other words, even if providing one or more newdictionaries to the user device 1002 would result in desirable speed andcompression for communications between the user device 1004 and server1002, the time it would take to send such one or more new dictionariesmay cause an undesirable delay which would outweigh implementation ofsuch new one or more new dictionaries.

Returning to the communications 1000 of FIG. 10, with a dictionary setselected 1010, the content is compressed 1012 via the selecteddictionary set and one or more dictionaries that are part of theselected dictionary set, but missing at the user device 1002 areidentified and sent 1016 to the user device 1002. The content data thatwas compressed via the selected dictionary set is sent 1018 to the userdevice 1002 and presented 1020.

As illustrated in the example of FIG. 10, the server 1004 can select aset of dictionaries to compress communications and provide one or moreof the dictionaries of the set to a user device 1002 so that thedictionaries become shared. For example, such dictionaries can includeone or more base dictionary, one or more sub-dictionary and/or one ormore snapshot dictionary. In contrast, FIG. 9 illustrates an example,where the server 904 selects dictionaries that are already sharedbetween the server 904 and user device 902. In further examples, ahybrid of these two examples can be used to communicate between a serverand user device.

For example, a server can identify a set of dictionaries (or identifiersand definitions) that are already shared by the server and a user deviceand also identify a set of dictionaries (or identifiers and definitions)that include at least a portion that is not currently shared by theserver and a user device. Instead of immediately encoding correspondencewith the unshared dictionaries and sending those unshared dictionariesto the user device, the server can instead first send communicationsencoded with the shared set of dictionaries while sending the unshareddictionaries, and then begin to send communications using the previouslyunshared dictionaries once the new dictionaries are received andimplemented at the user device. Accordingly, in some examples, theserver can send communications with currently shared dictionaries untilmore desirable dictionaries are sent to the user device during thesession. This can be desirable because it can allow initial content tobe obtained and presented by the user device without having to waituntil new dictionaries are received and implemented.

FIG. 11 illustrates a block diagram of a method 1100 for selecting oneor more dictionaries to compress content. In various examples, thismethod can be performed by the server 102, 804, 806, 904, 1004 of FIG.1, 8, 9, or 10. The method 1100 begins where a content request isreceived 1102 from a user device associated with a user account. Invarious examples, the user device can be the user device 104, 802, 902,1002 of FIG. 1, 8, 9, or 10.

The method 1100 continues where characteristics of the user device areidentified 1104. For example, characteristics of the user device caninclude, the type of device (e.g., smartphone, tablet computer,e-reader, wearable computer, desktop computer, or the like), chipset ofthe user device, CPU capabilities of the user device, memory capacity ofthe user device, display of the user device, audio capabilities of theuser device, operating system of the user device, geographic location ofthe user device, and the like.

Network characteristics can also be determined 1106, which can includebitrate, packet loss rate, bandwidth, type of network, communicationpath, location(s) of network, protocol(s) used by network, ISPsassociated with network, cost of network use, and the like. Networkcharacteristics can be determined in various suitable ways, which can bebased on current information about the network or can be implied orassumed based on various criteria. For example, a network condition canbe implied or assumed based on day and/or time (e.g., a given network isconsidered to be strained from 4:00 PM-7:30 PM on weekdays).Additionally user characteristics associated with the user accountassociated with the content request can be identified 1108, which caninclude user location, user browsing history, user search history, userpurchase history, gender, age, income, user account type, and the like.

One or more dictionaries can be selected 1110 to compress the requestedcontent based at least in part on characteristics of one or more of theuser device, network and user. In other words, in some examples, a setof one or more dictionaries can be selected to fulfill a request basedat least in part on various conditions, characteristics, capabilities,browsing history, previous dictionary use, previous dictionaryefficiency, or the like, associated with the content request. Forexample, network characteristics can affect the rate at whichsupplementary or additional dictionaries can be shared with a userdevice, and if a determination is made that the network is too slow totransmit large dictionaries, selection of dictionaries that are alreadyshared by the server and user device can be more desirable.

In another example, certain dictionaries may provide for faster orslower decoding at the user device based at least in part on theconfiguration, capabilities or status of the user device, and thereforea certain set of dictionaries can be selected for a given user devicebased at least in part on the speed at which the user device coulddecode or otherwise implement a certain set of dictionaries. Similarly,where a given user device has certain limitations, certain dictionariescan be used to provide greater compression without substantial loss ofperceived quality. For example, where a user device has a small or lowresolution display, images can be compressed to a lower resolution bycertain dictionaries, and the compression and lower resolutions may beunperceivable on the lower resolution screen.

In a further example, where a user has a history of browsing webpageshaving a certain class of content (e.g., the user likes to shop forshoes), a set of dictionaries can be selected which would perform betterbased at least in part on what sort of browsing the user is predicted toengage in during a given session. In yet another example, where webpagesare rendered differently based at least in part on a user account status(e.g., registered user, unregistered user, premium user) and thereforesome sets of dictionaries may provide more compression for differentuser account statuses. In yet another example, a webpage may be rendereddifferently based at least in part on location of the user and/or userdevice (e.g., due to language or content display limitations) andcertain sets of dictionaries may be selected based at least in part onhow webpages will be rendered based at least in part on user and/or userdevice location or detected user language settings.

FIG. 12 illustrates a block diagram of a method 1200 for modifying a setof dictionaries used during a communication session. In variousexamples, this method can be performed by the server 102, 804, 806, 904,1004 of FIG. 1, 8, 9, or 10. The method 1200 begins where use of a firstdictionary set is implemented 1202 during a user session. For example,the user session can be with a user device 104, 802, 902, 1002 of FIG.1, 8, 9, or 10. Additionally, the implementation 1202 can be via themethod 1100 of FIG. 11 or the like.

At 1204, a determination is made whether there has been any change inthe characteristics of any of a user device, network, or user associatedwith the user session. If not, the method 1200 continues to monitor forany such change and the method 1200 cycles at 1204. However, if such achange is detected, a determination is made, at 1206, whether such oneor more change alters the effectiveness of the first dictionary set1206. For example, if the user was browsing a first website where thefirst dictionary set provided optimal compression, and then the userbegins browsing a second website, the effectiveness (e.g., compressionor decoding rate) may be impacted in a negative way. If no change ineffectiveness is detected, at 1206, the method 1200 continues, to 1208,where use of the first dictionary set is maintained, and the method 1200then continues to monitor for changes in user device, network or usercharacteristics at 1204.

However, if a change in effectiveness is detected, at 1206, the method1200 continues to 1210 where a determination is made whether a seconddictionary set is available that meets replacement criteria. Forexample, where effectiveness of an implemented dictionary set isnegatively impacted, the server (or other device performing the method)can analyze other candidate sets of dictionaries that it has availableand also identify candidate sets of dictionaries that a user deviceassociated with the user session has access to or could have access toif the server (or other device) sent one or more new or supplementarydictionaries to the user device.

Replacement criteria can include a determination of whether replacementof the first set would result in substantially increased compression ofcommunications. For example, where compression is decreased or stays thesame, replacement may not be desirable. Similarly, where compression isonly slightly or insubstantially increased, overhead associated withreplacing the first dictionary with another dictionary may cause a givencandidate dictionary set to not meet replacement criteria. Additionally,where one or more dictionaries needs to be sent to the user device toachieve improved compression, if such sending would be time and/orresource consuming such that presenting content was negatively impactedin terms of quality or time, then such a candidate dictionary set maynot meet replacement criteria.

Where a second dictionary set is not available that meets replacementcriteria, then the method 1200 continues, to 1208, where use of thefirst dictionary set is maintained, and the method 1200 then continuesto monitor for changes in user device, network or user characteristicsat 1204. However, if a second dictionary set is available that meetsreplacement criteria, then the method 1200 continues, to 1212, where thefirst dictionary is replaced with the second dictionary set for useduring the user session.

In various examples, a plurality of sets of dictionaries can be usedsimultaneously during a communication session. For example, a first setof dictionaries can be used to compress HTML code, a second set ofdictionaries can be used to compress Java script, and a third set ofdictionaries can be used to compress CSS. Alternatively, different setsof dictionaries can be used for different types of content orcommunications. For example, when a user is viewing a shopping cart of awebsite, a first set of dictionaries can be used, whereas where a useris viewing a “wish list” of items of a website, a second set ofdictionaries can be used. In such examples, replacing a dictionary canrefer to replacing one of the plurality of sets being used for aspecific purpose with a dictionary that better fits that specificpurpose.

FIG. 13 illustrates a method 300 for generating and selecting adictionary. In various examples, this method 1300 can be performed bythe server 102, 804, 806, 904, 1004 of FIG. 1, 8, 9, or 10. The method300 begins where a number of candidate dictionaries for generation isselected 1302 and a corpus of content is obtained 1304. For example, acorpus of content can include various types of suitable contentincluding a plurality of webpages, documents, images, videos, text,audio, software code, and the like. In some examples, the corpus ofcontent can include a plurality of content types, and in other examples,the corpus of content can be limited to a single type of content. In oneexample, a set of website traffic can be used as a corpus of content andsuch traffic can be filtered based at least in part on various criteriaincluding user type, user location, user device type, user operatingsystem type, user browser type, user browsing history, and the like.

At looping block 1306, a loop begins for each dictionary being created.In other words, the steps of the loop can occur for each of thedictionaries selected 1302 for generation. The loop begins where acontent corpus subset is generated 1308. For example, where a set ofwebsite traffic comprises the obtained corpus of content, a randomsubset of this website traffic can be selected for generating 138 thecorpus subset with such a subset being any suitable portion of thecorpus, including 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, and the like.

Returning to the loop, a dictionary is generated 1310 based at least inpart on the subset of the corpus. Generating 1310 a dictionary can bedone in various suitable ways. For example, the corpus subset can beanalyzed for common strings of various sizes and a set of identifiersand definitions based at least in part on identified common strings canbe generated. Selection of which common or repeated strings should beincluded in a dictionary can be based at least in part on the length ofthe string, number of times the string appears in the corpus, and thelike.

Returning to the method 1300, the generated dictionary is used 1312 tocompress the full corpus of content and quality metrics for thegenerated dictionary based at least in part on compression of the fullcorpus of content are identified 1314. For example, quality metrics caninclude compression speed, size of full corpus before and aftercompression with the dictionary, size of the dictionary, and the like.

The loop for each dictionary being generated ends at looping block 1316and a determination is made whether one or more of the generateddictionaries meet candidate criteria. Where one or more dictionariesmeet selection criteria, these dictionaries are selected 1320. However,if no generated dictionaries meet selection criteria, then the one ormore generated dictionaries are rejected 1322.

The identified 1314 dictionary quality metrics can be used to comparethe candidate dictionaries to rank the generated dictionaries.Additionally, such dictionaries can be compared other dictionaries thatare currently being used or that were previously generated. For example,candidate criteria can include selecting a dictionary that has qualitymetrics that are better than any dictionary currently being used. Inother words, generated dictionaries may only be useful if suchdictionaries perform better than existing dictionaries.

As discussed above, quality metrics can include compression speed, sizeof full corpus before and after compression with the dictionary, size ofthe dictionary, and the like, and therefore candidate criteria can bebased at least in part on one or more of such quality metrics. Forexample, where a candidate dictionary provides less compression than acurrently implemented dictionary, but is one tenth the size of thecurrently implemented dictionary, then the candidate dictionary maystill be desirable. Similarly, where a candidate dictionary providesless compression than a currently implemented dictionary, butcompression and/or decompression using the dictionary takes one tenth ofthe time of the currently implemented dictionary, then the candidatedictionary may still be desirable. Accordingly, in various examples,although compression ratio of a dictionary can be one desirablecharacteristic for selection criteria, various other criteria can beused to select desirable dictionary candidates.

Additionally, candidate dictionaries can be generated that are basedictionaries or sub-dictionaries. In other words, in some examples,candidate dictionaries can be generated which are based at least in parton or dependent upon a base dictionary or can be generated without anydependencies or associations with other dictionaries.

Dictionaries can be generated and used in various suitable ways. In oneexample, a website administrator can generate dictionaries to compresswebsite content and new dictionaries can be generated over time as thewebsite content changes, as user interaction with the website changes,as network specification change, and as methods for generatingdictionaries change. Accordingly, in some examples, a company can useits own current content as a corpus of content that can be used togenerate and test dictionaries that may be used to replace one or moredictionaries currently being used.

In further examples, a service provider can generate one or moredictionaries for a customer. In other words, a service provide canprovide dictionary generation as a service to customers. For example,FIG. 14 illustrates a method 1400 of generating a dictionary, which canbe used by a service provider to generate one or more dictionaries as aservice. In various examples, this method 1400 can be performed by theserver 102, 804, 806, 904, 1004 of FIG. 1, 8, 9, or 10.

The method 1400 begins where a content corpus is received 1402. Asdiscussed in various examples of this disclosure, a content corpus caninclude various types of content including a plurality of webpages,documents, images, videos, text, audio, software code, and the like.Such a content corpus can be selected and provided by a customer to adictionary generation service provider in various suitable ways,including granting the service provider access to content streams,providing one or more indicator of selected content, sending content, orthe like.

The method 1400 continues where a compression type selection is received1404 and where a dictionary size range selection is received 1406. Invarious examples a compression type can include a compression protocol,compression format, or the like. A dictionary size range selection caninclude a selection of the total size of the dictionary, a selection ofthe number of identifiers and definitions of a dictionary, the size orlength of definitions and/or identifiers of a dictionary, or the like.Additionally, in some examples a size range can include a number and/orsize of sub-dictionaries and/or based dictionaries and a size of allsuch sub-dictionaries and based dictionaries combined.

The method 1400 continues where a selection of candidate dictionaryranking criteria is received 1408. In some examples, such candidatedictionary ranking criteria can include compression speed, size of fullcorpus before and after compression with the dictionary, size of thedictionary, and the like. For example, a given customer may havedifferent priorities based at least in part on the use of thedictionary, network in which a dictionary is used, users that user thedictionary, device(s) using the dictionary, and the like. For example,where a customer intends to use a dictionary (or set of dictionaries)with user devices having weak CPUs, the customer can prioritizegeneration of dictionaries that will be provide for fast decoding ofcontent, even user devices having limited capabilities.

Alternatively, where a user intents to use a set of dictionaries withuser devices where a base dictionary is shipped with the user device.The customer can select generation of a large base dictionary, which mayor may not be updatable with sub-dictionaries. In this same example,where such user devices will likely be used on a network having limitedbandwidth, the customer can select generation of sub-dictionaries thatare small so that such sub-dictionaries can be communicated to the userdevices even via the limited network.

Returning to the method 1400, at least one dictionary is generated 1410based at least in part on the selected compression type, size range andranking criteria. In some examples, the generated dictionaries can be aset of candidate dictionaries. In other words, alternative versions ofone or more dictionaries can be generated for a customer. Additionally,as discussed in various examples of this disclosure a generateddictionary set can include one or more base dictionary, sub-dictionary,snapshot dictionary, and the like. In one example the dictionary isgenerated 1410 via a method comprising steps illustrated in FIG. 13.

FIG. 15 illustrates a method 1500 of monitoring the effectiveness of animplemented first dictionary and replacing it with a generated seconddictionary when a replacement threshold is exceeded. In variousexamples, this method 1400 can be performed by the server 102, 804, 806,904, 1004 of FIG. 1, 8, 9, or 10. The method 1500 begins where use of afirst dictionary is implemented 1502 and the effectiveness of the firstdictionary is monitored 1504 based at least in part on a set ofperformance criteria. Such monitoring can occur at regular intervals, inreal time, or in near real time. For example, a “daily best” dictionaryor dictionary set can be generated. Additionally, in some examples,certain events can trigger monitoring or review of a current dictionaryset. For example, when a new website build occurs, the currentlyimplemented dictionary can be evaluated for effectiveness.

Performance criteria can be associated with various metrics related toperformance of a dictionary, including compression speed, size of fullcorpus before and after compression with the dictionary, size of thedictionary, and the like. For example, as network conditions change,user interaction with content changes, or as the content beingcompressed by the dictionary changes, the performance of the dictionarycan change over time. In various examples, the first dictionary may havebeen tailored to content of a certain type, network condition of acertain type, or the like and this dictionary may become less effectiveover time.

Returning to the method 1500, a set of one or more candidatedictionaries is generated 1500 based at least in part on a contentstream and the effectiveness of the one or more dictionaries can bedetermined 1508 based at least in part on a set of performance criteria,which can include the performance criteria discussed above. In someexamples, the same performance criteria used to monitor theeffectiveness of the first dictionary are used to determine theeffectiveness of the one or more candidate dictionary.

The candidate effectiveness is compared 1510 to the effectiveness of thefirst dictionary, and at 1512 a determination is made whether one ormore of the generated candidate dictionaries exceed a replacementthreshold. A replacement threshold can include various factors,including a determination of whether replacement of the first dictionarywould result in substantially increased compression of communications.For example, where compression is decreased or stays the same,replacement may not be desirable. Similarly, where compression is onlyslightly or insubstantially increased, overhead associated withreplacing the first dictionary with another dictionary may cause a givencandidate dictionary set to not meet replacement criteria. Additionally,where one or more dictionaries need to be sent to the user device toachieve improved compression, if such sending would be time and/orresource consuming such that presenting content was negatively impactedin terms of quality or time, then such a candidate dictionary exceed areplacement threshold. Where the replacement threshold is exceeded, thefirst dictionary is replaced 1514 with one or more generated dictionarythat exceeds the threshold. However, if the replacement threshold is notexceeded, then implementation of the first dictionary is maintained1516.

FIG. 16 illustrates aspects of an example environment 1600 forimplementing aspects in accordance with various examples. As will beappreciated, although a web-based environment is used for purposes ofexplanation, different environments may be used, as appropriate, toimplement various examples. The environment includes an electronicclient device 1602, which can include any appropriate device operable tosend and/or receive requests, messages, or information over anappropriate network 1604 and, in some examples, convey information backto a user of the device. Examples of such client devices includepersonal computers, cell phones, handheld messaging devices, laptopcomputers, tablet computers, set-top boxes, personal data assistants,embedded computer systems, electronic book readers, and the like. Thenetwork can include any appropriate network, including an intranet, theInternet, a cellular network, a local area network, a satellite networkor any other such network and/or combination thereof. Components usedfor such a system can depend at least in part upon the type of networkand/or environment selected. Many protocols and components forcommunicating via such a network are well known and will not bediscussed herein in detail. Communication over the network can beenabled by wired or wireless connections and combinations thereof. Inthis example, the network includes the Internet and/or otherpublicly-addressable communications network, as the environment includesa web server 1606 for receiving requests and serving content in responsethereto, although for other networks an alternative device serving asimilar purpose could be used as would be apparent to one of ordinaryskill in the art.

The illustrative environment includes at least one application server1608 and a data store 1610. It should be understood that there can beseveral application servers, layers or other elements, processes orcomponents, which may be chained or otherwise configured, which caninteract to perform tasks such as obtaining data from an appropriatedata store. Servers, as used herein, may be implemented in various ways,such as hardware devices or virtual computer systems. In some contexts,servers may refer to a programming module being executed on a computersystem. As used herein, unless otherwise stated or clear from context,the term “data store” refers to any device or combination of devicescapable of storing, accessing, and retrieving data, which may includeany combination and number of data servers, databases, data storagedevices, and data storage media, in any standard, distributed, virtual,or clustered environment. The application server can include anyappropriate hardware, software, and firmware for integrating with thedata store as needed to execute aspects of one or more applications forthe client device, handling some or all of the data access and businesslogic for an application. The application server may provide accesscontrol services in cooperation with the data store and is able togenerate content including, but not limited to, text, graphics, audio,video, and/or other content usable to be provided to the user, which maybe served to the user by the web server in the form of HyperText MarkupLanguage (“HTML”), Extensible Markup Language (“XML”), JavaScript,Cascading Style Sheets (“CSS”), JavaScript Object Notation (JSON),and/or another appropriate client-side structured language. Contenttransferred to a client device may be processed by the client device toprovide the content in one or more forms including, but not limited to,forms that are perceptible to the user audibly, visually, and/or throughother senses. The handling of all requests and responses, as well as thedelivery of content between the client device 1602 and the applicationserver 1608, can be handled by the web server using PHP: HypertextPreprocessor (“PHP”), Python, Ruby, Perl, Java, HTML, XML, JSON, and/oranother appropriate server-side structured language in this example.Further, operations described herein as being performed by a singledevice may, unless otherwise clear from context, be performedcollectively by multiple devices, which may form a distributed and/orvirtual system.

The data store 1610 can include several separate data tables, databases,data documents, dynamic data storage schemes and/or other data storagemechanisms and media for storing data relating to a particular aspect ofthe present disclosure. For example, the data store illustrated mayinclude mechanisms for storing production data 1612 and user information1616, which can be used to serve content for the production side. Thedata store also is shown to include a mechanism for storing log data1614, which can be used for reporting, analysis or other such purposes.It should be understood that there can be many other aspects that mayneed to be stored in the data store, such as page image information andaccess rights information, which can be stored in any of the abovelisted mechanisms as appropriate or in additional mechanisms in the datastore 1610. The data store 1610 is operable, through logic associatedtherewith, to receive instructions from the application server 1608 andobtain, update or otherwise process data in response thereto. Theapplication server 1608 may provide static, dynamic, or a combination ofstatic and dynamic data in response to the received instructions.Dynamic data, such as data used in web logs (blogs), shoppingapplications, news services and other such applications may be generatedby server-side structured languages as described herein or may beprovided by a content management system (“CMS”) operating on, or underthe control of, the application server. In one example, a user, througha device operated by the user, might submit a search request for acertain type of item. In this case, the data store might access the userinformation to verify the identity of the user and can access thecatalog detail information to obtain information about items of thattype. The information then can be returned to the user, such as in aresults listing on a web page that the user is able to view via abrowser on the user device 1602. Information for a particular item ofinterest can be viewed in a dedicated page or window of the browser. Itshould be noted, however, that examples of the present disclosure arenot necessarily limited to the context of web pages, but may be moregenerally applicable to processing requests in general, where therequests are not necessarily requests for content.

Each server typically will include an operating system that providesexecutable program instructions for the general administration andoperation of that server and typically will include a computer-readablestorage medium (e.g., a hard disk, random access memory, read onlymemory, etc.) storing instructions that, when executed (i.e., as aresult of being executed) by a processor of the server, allow the serverto perform its intended functions.

The environment, in one example, is a distributed and/or virtualcomputing environment utilizing several computer systems and componentsthat are interconnected via communication links, using one or morecomputer networks or direct connections. However, it will be appreciatedby those of ordinary skill in the art that such a system could operateequally well in a system having fewer or a greater number of componentsthan are illustrated in FIG. 16. Thus, the depiction of the system 1600in FIG. 16 should be taken as being illustrative in nature and notlimiting to the scope of the disclosure.

The various examples further can be implemented in a wide variety ofoperating environments, which in some cases can include one or more usercomputers, computing devices or processing devices which can be used tooperate any of a number of applications. User or client devices caninclude any of a number of computers, such as desktop, laptop, or tabletcomputers running a standard operating system, as well as cellular,wireless, and handheld devices running mobile software and capable ofsupporting a number of networking and messaging protocols. Such a systemalso can include a number of workstations running any of a variety ofcommercially-available operating systems and other known applicationsfor purposes such as development and database management. These devicesalso can include other electronic devices, such as dummy terminals,thin-clients, gaming systems, and other devices capable of communicatingvia a network. These devices also can include virtual devices such asvirtual machines, hypervisors, and other virtual devices capable ofcommunicating via a network.

Various examples of the present disclosure utilize at least one networkthat would be familiar to those skilled in the art for supportingcommunications using any of a variety of commercially-availableprotocols, such as Transmission Control Protocol/Internet Protocol(“TCP/IP”), User Datagram Protocol (“UDP”), protocols operating invarious layers of the Open System Interconnection (“OSI”) model, FileTransfer Protocol (“FTP”), Universal Plug and Play (“UpnP”), NetworkFile System (“NFS”), Common Internet File System (“CIFS”), andAppleTalk. The network can be, for example, a local area network, awide-area network, a virtual private network, the Internet, an intranet,an extranet, a public switched telephone network, an infrared network, awireless network, a satellite network, and any combination thereof. Insome examples, connection-oriented protocols may be used to communicatebetween network endpoints. Connection-oriented protocols (sometimescalled connection-based protocols) are capable of transmitting data inan ordered stream. Connection-oriented protocols can be reliable orunreliable. For example, the TCP protocol is a reliableconnection-oriented protocol. Asynchronous Transfer Mode (“ATM”) andFrame Relay are unreliable connection-oriented protocols.Connection-oriented protocols are in contrast to packet-orientedprotocols such as UDP that transmit packets without a guaranteedordering.

In examples utilizing a web server, the web server can run any of avariety of server or mid-tier applications, including Hypertext TransferProtocol (“HTTP”) servers, FTP servers, Common Gateway Interface (“CGI”)servers, data servers, Java servers, Apache servers, and businessapplication servers. The server(s) also may be capable of executingprograms or scripts in response to requests from user devices, such asby executing one or more web applications that may be implemented as oneor more scripts or programs written in any programming language, such asJava®, C, C#, or C++, or any scripting language, such as Ruby, PHP,Perl, Python, or TCL, as well as combinations thereof. The server(s) mayalso include database servers, including without limitation thosecommercially available from Oracle®, Microsoft®, Sybase®, and IBM® aswell as open-source servers such as MySQL, Postgres, SQLite, MongoDB,and any other server capable of storing, retrieving, and accessingstructured or unstructured data. Database servers may includetable-based servers, document-based servers, unstructured servers,relational servers, non-relational servers or combinations of these,and/or other database servers.

The environment can include a variety of data stores and other memoryand storage media as discussed above. These can reside in a variety oflocations, such as on a storage medium local to (and/or resident in) oneor more of the computers or remote from any or all of the computersacross the network. In a particular set of examples, the information mayreside in a storage-area network (“SAN”) familiar to those skilled inthe art. Similarly, any necessary files for performing the functionsattributed to the computers, servers or other network devices may bestored locally and/or remotely, as appropriate. Where a system includescomputerized devices, each such device can include hardware elementsthat may be electrically coupled via a bus, the elements including, forexample, at least one central processing unit (“CPU” or “processor”), atleast one input device (e.g., a mouse, keyboard, controller, touchscreen or keypad) and at least one output device (e.g., a displaydevice, printer, or speaker). Such a system may also include one or morestorage devices, such as disk drives, optical storage devices andsolid-state storage devices such as random access memory (“RAM”) orread-only memory (“ROM”), as well as removable media devices, memorycards, flash cards, etc.

Such devices also can include a computer-readable storage media reader,a communications device (e.g., a modem, a network card (wireless orwired), an infrared communication device, etc.), and working memory asdescribed above. The computer-readable storage media reader can beconnected with, or configured to receive, a computer-readable storagemedium, representing remote, local, fixed, and/or removable storagedevices as well as storage media for temporarily and/or more permanentlycontaining, storing, transmitting, and retrieving computer-readableinformation. The system and various devices also typically will includea number of software applications, modules, services or other elementslocated within at least one working memory device, including anoperating system and application programs, such as a client applicationor web browser. In addition, customized hardware might also be usedand/or particular elements might be implemented in hardware, software(including portable software, such as applets), or both. Further,connection to other computing devices such as network input/outputdevices may be employed.

Storage media and computer readable media for containing code, orportions of code, can include any appropriate media known or used in theart, including storage media and communication media, such as, but notlimited to, volatile and non-volatile, removable and non-removable mediaimplemented in any method or technology for storage and/or transmissionof information such as computer readable instructions, data structures,program modules, or other data, including RAM, ROM, ElectricallyErasable Programmable Read-Only Memory (“EEPROM”), flash memory or othermemory technology, Compact Disc Read-Only Memory (“CD-ROM”), digitalversatile disk (DVD) or other optical storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other medium which can be used to store the desired informationand which can be accessed by the system device. Based on the disclosureand teachings provided herein, a person of ordinary skill in the artwill appreciate other ways and/or methods to implement the variousexamples.

The specification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense. It will, however, beevident that various modifications and changes may be made thereuntowithout departing from the broader spirit and scope of the invention asset forth in the claims.

Other variations are within the spirit of the present disclosure. Thus,while the disclosed techniques are susceptible to various modificationsand alternative constructions, certain illustrated examples thereof areshown in the drawings and have been described above in detail. It shouldbe understood, however, that there is no intention to limit theinvention to the specific form or forms disclosed, but on the contrary,the intention is to cover all modifications, alternative constructionsand equivalents falling within the spirit and scope of the invention, asdefined in the appended claims.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the disclosed examples (especially in the contextof the following claims) are to be construed to cover both the singularand the plural, unless otherwise indicated herein or clearlycontradicted by context. The terms “comprising,” “having,” “including,”and “containing” are to be construed as open-ended terms (i.e., meaning“including, but not limited to,”) unless otherwise noted. The term“connected,” when unmodified and referring to physical connections, isto be construed as partly or wholly contained within, attached to orjoined together, even if there is something intervening. Recitation ofranges of values herein are merely intended to serve as a shorthandmethod of referring individually to each separate value falling withinthe range, unless otherwise indicated herein and each separate value isincorporated into the specification as if it were individually recitedherein. The use of the term “set” (e.g., “a set of items”) or “subset”unless otherwise noted or contradicted by context, is to be construed asa nonempty collection comprising one or more members. Further, unlessotherwise noted or contradicted by context, the term “subset” of acorresponding set does not necessarily denote a proper subset of thecorresponding set, but the subset and the corresponding set may beequal.

Conjunctive language, such as phrases of the form “at least one of A, B,and C,” or “at least one of A, B and C,” unless specifically statedotherwise or otherwise clearly contradicted by context, is otherwiseunderstood with the context as used in general to present that an item,term, etc., may be either A or B or C, or any nonempty subset of the setof A and B and C. For instance, in the illustrative example of a sethaving three members, the conjunctive phrases “at least one of A, B, andC” and “at least one of A, B and C” refer to any of the following sets:{A}, {B}, {C}, {A, B}, {A, C}, {B, C}, {A, B, C}. Thus, such conjunctivelanguage is not generally intended to imply that certain examplesrequire at least one of A, at least one of B and at least one of C eachto be present.

Operations of processes described herein can be performed in anysuitable order unless otherwise indicated herein or otherwise clearlycontradicted by context. Processes described herein (or variationsand/or combinations thereof) may be performed under the control of oneor more computer systems configured with executable instructions and maybe implemented as code (e.g., executable instructions, one or morecomputer programs or one or more applications) executing collectively onone or more processors, by hardware or combinations thereof. The codemay be stored on a computer-readable storage medium, for example, in theform of a computer program comprising a plurality of instructionsexecutable by one or more processors. The computer-readable storagemedium may be non-transitory. In some examples, the code is stored onset of one or more non-transitory computer-readable storage media havingstored thereon executable instructions that, when executed (i.e., as aresult of being executed) by one or more processors of a computersystem, cause the computer system to perform operations describedherein. The set of non-transitory computer-readable storage media maycomprise multiple non-transitory computer-readable storage media and oneor more of individual non-transitory storage media of the multiplenon-transitory computer-readable storage media may lack all of the codewhile the multiple non-transitory computer-readable storage mediacollectively store all of the code.

Accordingly, in some examples, computer systems are configured toimplement one or more services that singly or collectively performoperations of processes described herein. Such computer systems may, forinstance, be configured with applicable hardware and/or software thatenable the performance of the operations. Further, computer systems thatimplement various examples of the present disclosure may, in someexamples, be single devices and, in other examples, be distributedcomputer systems comprising multiple devices that operate differentlysuch that the distributed computer system performs the operationsdescribed herein and such that a single device may not perform alloperations.

The use of any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate examples of theinvention and does not pose a limitation on the scope of the inventionunless otherwise claimed. No language in the specification should beconstrued as indicating any non-claimed element as essential to thepractice of the invention.

Examples of this disclosure are described herein, including the bestmode known to the inventors for carrying out the invention. Variationsof those examples may become apparent to those of ordinary skill in theart upon reading the foregoing description. The inventors expect skilledartisans to employ such variations as appropriate and the inventorsintend for examples of the present disclosure to be practiced otherwisethan as specifically described herein. Accordingly, the scope of thepresent disclosure includes all modifications and equivalents of thesubject matter recited in the claims appended hereto as permitted byapplicable law. Moreover, any combination of the above-describedelements in all possible variations thereof is encompassed by the scopeof the present disclosure unless otherwise indicated herein or otherwiseclearly contradicted by context.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

What is claimed is:
 1. A computer-implemented method for generatingcompression dictionary snapshots, comprising: under the control of oneor more computer systems configured with executable instructions,obtaining a snapshot manifest, the snapshot manifest including locationinformation for a set of dictionary portions of a compressiondictionary, the location information indicating an identity of aprevious snapshot and a location of the dictionary portions within theprevious snapshot, and the dictionary portions comprising one or moredefinitions; incrementing a snapshot count; determining a first subsetof dictionary portions, the first subset of dictionary portionscomprising dictionary portions of the set of dictionary portions thatare new or have changed since a time of a most recent previous snapshot;determining, from the snapshot manifest, a second subset of dictionaryportions based at least in part on a snapshot depth and the snapshotcount; obtaining the first and second subsets of dictionary portions;generating at least a snapshot update of the set of dictionary portionsbased at least in part on the obtained subsets of dictionary portions;and storing the at least a snapshot update of the set of dictionaryportions.
 2. The computer-implemented method of claim 1, wherein thecompression dictionary is defined by one or more base dictionaries andone or more sub-dictionaries.
 3. The computer-implemented method ofclaim 1, wherein the snapshot manifest is a first snapshot manifest andthe method further comprises: receiving a request to restore the set ofdictionary portions to a particular location; obtaining a secondsnapshot manifest, the second snapshot manifest including locations ofdictionary portions of the obtained first and second subsets ofdictionary portions in the at least a snapshot update; and iteratingthrough the locations of dictionary portions indicated in the secondsnapshot manifest and copying the dictionary portions from the indicatedlocations to the particular location.
 4. The computer-implemented methodof claim 1, further comprising: selecting a first set of compressiondictionaries to compress content requested by a user device based atleast in part on a second set of compression dictionaries available atthe user device and a third set of locally available compressiondictionaries that includes the at least a snapshot update of the set ofdictionary portions; and sending the at least a snapshot update of theset of dictionary portions to the user device at least based on theselecting of the first set of compression dictionaries.
 5. A system,comprising: memory storing a dictionary defining a set of definitions;one or more processors; memory including instructions that, whenexecuted by the one or more processors, cause the system to: generate aset of snapshots by causing the system to: determine a subset of the setof definitions, the subset comprising: a first subset comprising one ormore definitions that have changed since a time of a previous snapshot;and a second subset comprising one or more definitions associated with apredetermined portion of the dictionary; and generate and store thesnapshots based at least in part on the determined subset of one or moredefinitions; and determine the plurality of active snapshots from theset of snapshots such that the set of one or more definitions isincluded in the plurality of active snapshots.
 6. The system of claim 5,wherein: the subset is the first subset; and the instructions furtherinclude instructions that cause the system to: receive a request torestore a second subset of the set of one or more definitions to astorage location; and in response to receiving the request, obtaindefinitions of the second subset from at least one of the plurality ofactive snapshots and store the one or more definitions at the storagelocation.
 7. The system of claim 5, wherein: selecting a first set ofcompression dictionaries to compress communications with a device basedat least in part on a second set of compression dictionaries availableat the device and a third set of locally available compressiondictionaries that includes the plurality of active snapshots; andsending the at least a portion of the plurality of active snapshots tothe device for use in compression of communications with the device. 8.The system of claim 5, wherein the instructions that cause the system togenerate and store snapshots includes instructions that cause the systemto: obtain the first subset of one or more definitions from thedictionary; obtain the second subset of one or more definitions, whereinat least a portion of the second subset of one or more definitions isobtained from a previously generated active snapshot of the plurality ofactive snapshots; generate the snapshot based at least in part on theobtained first and second subsets of one or more definitions; and storethe snapshot for use in compression of communications between a deviceand server.
 9. The system of claim 5, wherein the instructions furtherinclude instructions that cause the system to send the plurality ofactive snapshots to a user device so that the user device and systemshare a common set of definitions used by the system to compress a setof communications and used by the user device to decompress the set ofcommunications.
 10. The system of claim 5, wherein the instructions thatcause the system to determine the subset of the set of one or moredefinitions include instructions that cause the system to obtain amanifest that indicates an identity and location for definitionsrequired to restore the dictionary to a state of the dictionary at atime corresponding to the snapshot, the manifest comprising: a firstidentity and location in the dictionary for definitions in the firstsubset of one or more definitions; and a second identity and location inthe plurality of active snapshots for definitions in the second subsetof one or more definitions.
 11. The system of claim 5, wherein theinstructions further include instructions that cause the system to:generate a current state of the dictionary based at least in part on aportion of the plurality snapshots to result in an updated dictionary;and send the updated dictionary to a user device for use in compressionof communications with the user device.
 12. The system of claim 5,wherein the dictionary is defined by one or more base dictionaries andone or more sub-dictionaries that depends from a base dictionary.
 13. Anon-transitory computer-readable storage medium having stored thereonexecutable instructions that, when executed by one or more processors ofa computer system, cause the computer system to at least: determine afirst set of one or more definitions including one or more definitionsthat have changed since a time of a previous snapshot; determine asecond set of one or more definitions based at least in part on apredetermined amount; generate at least one snapshot update of adictionary based at least in part on a combination of the first set ofone or more definitions and the second set of one or more definitions;and store the at least one snapshot update for use in compressingcommunications.
 14. The non-transitory computer-readable storage mediumof claim 13, wherein the instructions further include instructions that,when executed by the one or more processors, cause the computer systemto: receive a request to restore at least a portion of a dictionary to aprevious state; determine a third set of one or more definitions definedby the dictionary, the third set of one or more definitions includingone or more definitions from the combination of the first set of one ormore definitions and the second set of one or more definitions; obtainthe third set of one or more definitions in part from the at least onesnapshot update; and restore the dictionary by storing the obtainedthird set of one or more definitions.
 15. The non-transitorycomputer-readable storage medium of claim 13, wherein the first set andthe second set are disjoint sets.
 16. The non-transitorycomputer-readable storage medium of claim 13, wherein the instructionsthat cause the computer system to generate the at least one snapshotupdate include instructions that cause the computer system to: obtainthe first set of one or more definitions from a dictionary defining aplurality of definitions; obtain the second set of one or moredefinitions, wherein at least a subset of the second set of one or moredefinitions are obtained from a previously generated snapshot update;and generate the at least one snapshot update at least in part from theobtained first and second sets of one or more definitions.
 17. Thenon-transitory computer-readable storage medium of claim 13, wherein theinstructions that cause the computer system to determine the second setof one or more definitions further include instructions that cause thecomputer system to exclude a definition from the second set of one ormore definitions if the determined first set of one or more definitionsincludes a same definition as the definition.
 18. The non-transitorycomputer-readable storage medium of claim 13, wherein the instructionsfurther include instructions that cause the computer system to: select afirst set of compression dictionaries to compress communications with adevice based at least in part on a second set of compressiondictionaries available at the device and a third set of locallyavailable compression dictionaries that includes the at least onesnapshot update; and send the at least one snapshot update to the devicefor use in compression of communications with the device.
 19. Thenon-transitory computer-readable storage medium of claim 13, wherein theinstructions further cause the computer system to send a of activesnapshots to a user device so that the user device and system share acommon set of definitions used by the system to compress a set ofcommunications and used by the user device to decompress the set ofcommunications.
 20. The non-transitory computer-readable storage mediumof claim 13, wherein the instructions that cause the computer system todetermine the second set of one or more definitions include instructionsthat cause the computer system to: increment a snapshot count; obtain amanifest that includes an entry for definitions of the dictionary; anddetermine the second set of one or more definitions based at least inpart on the manifest, the snapshot count, and a snapshot depth.